2191720401 has 12 divisors (see below), whose sum is σ = 3409343028. Its totient is φ = 1348750944.

The previous prime is 2191720387. The next prime is 2191720441. The reversal of 2191720401 is 1040271912.

2191720401 is a `hidden beast` number, since 2 + 191 + 72 + 0 + 401 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 315098001 + 1876622400 = 17751^2 + 43320^2 .

It is not a de Polignac number, because 2191720401 - 2⁵ = 2191720369 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2191720441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9366210 + ... + 9366443.

It is an arithmetic number, because the mean of its divisors is an integer number (284111919).

Almost surely, 2^2191720401 is an apocalyptic number.

It is an amenable number.

2191720401 is a deficient number, since it is larger than the sum of its proper divisors (1217622627).

2191720401 is a wasteful number, since it uses less digits than its factorization.

2191720401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18732672 (or 18732669 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 2191720401 is about 46815.8135783199. The cubic root of 2191720401 is about 1298.9578237119.

Subtracting from 2191720401 its reverse (1040271912), we obtain a square (1151448489 = 33933²).

The spelling of 2191720401 in words is "two billion, one hundred ninety-one million, seven hundred twenty thousand, four hundred one".