21699957 has 24 divisors (see below), whose sum is σ = 31352160. Its totient is φ = 13309920.

The previous prime is 21699901. The next prime is 21700001. The reversal of 21699957 is 75999612.

It is not a de Polignac number, because 21699957 - 2¹⁰ = 21698933 is a prime.

Its product of digits (306180) is a multiple of the sum of its prime divisors (162).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21699857) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 274644 + ... + 274722.

It is an arithmetic number, because the mean of its divisors is an integer number (1306340).

Almost surely, 2^21699957 is an apocalyptic number.

It is an amenable number.

21699957 is a deficient number, since it is larger than the sum of its proper divisors (9652203).

21699957 is an equidigital number, since it uses as much as digits as its factorization.

21699957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241 (or 162 counting only the distinct ones).

The product of its digits is 306180, while the sum is 48.

The square root of 21699957 is about 4658.3212641466. The cubic root of 21699957 is about 278.9242609896.

The spelling of 21699957 in words is "twenty-one million, six hundred ninety-nine thousand, nine hundred fifty-seven".