21197861 has 12 divisors (see below), whose sum is σ = 23080260. Its totient is φ = 19453440.

The previous prime is 21197857. The next prime is 21197867. The reversal of 21197861 is 16879112.

It can be written as a sum of positive squares in 6 ways, for example, as 1705636 + 19492225 = 1306^2 + 4415^2 .

It is not a de Polignac number, because 21197861 - 2² = 21197857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21197867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10955 + ... + 12743.

It is an arithmetic number, because the mean of its divisors is an integer number (1923355).

Almost surely, 2^21197861 is an apocalyptic number.

It is an amenable number.

21197861 is a deficient number, since it is larger than the sum of its proper divisors (1882399).

21197861 is a wasteful number, since it uses less digits than its factorization.

21197861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1864 (or 1847 counting only the distinct ones).

The product of its digits is 6048, while the sum is 35.

The square root of 21197861 is about 4604.1134868724. The cubic root of 21197861 is about 276.7561922176.

The spelling of 21197861 in words is "twenty-one million, one hundred ninety-seven thousand, eight hundred sixty-one".