2191644225 has 27 divisors (see below), whose sum is σ = 3926736489. Its totient is φ = 1168502400.

The previous prime is 2191644193. The next prime is 2191644229. The reversal of 2191644225 is 5224461912.

It is a happy number.

The square root of 2191644225 is 46815.

It is a perfect power (a square), and thus also a powerful number.

2191644225 is a `hidden beast` number, since 2 + 1 + 9 + 1 + 644 + 2 + 2 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 1349019441 + 842624784 = 36729^2 + 29028^2 .

It is not a de Polignac number, because 2191644225 - 2⁵ = 2191644193 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 2191644225.

It is not an unprimeable number, because it can be changed into a prime (2191644229) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 700665 + ... + 703785.

Almost surely, 2^2191644225 is an apocalyptic number.

2191644225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

2191644225 is the 46815-th square number.

2191644225 is the 23408-th centered octagonal number.

It is an amenable number.

2191644225 is a deficient number, since it is larger than the sum of its proper divisors (1735092264).

2191644225 is an frugal number, since it uses more digits than its factorization.

2191644225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6258 (or 3129 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The cubic root of 2191644225 is about 1298.9427745664.

Multiplying 2191644225 by its sum of digits (36), we get a square (78899192100 = 280890²).

It can be divided in two parts, 2191 and 644225, that added together give a square (646416 = 804²).

The spelling of 2191644225 in words is "two billion, one hundred ninety-one million, six hundred forty-four thousand, two hundred twenty-five".