21557913 has 32 divisors (see below), whose sum is σ = 33331200. Its totient is φ = 12280896.

The previous prime is 21557843. The next prime is 21557917. The reversal of 21557913 is 31975512.

It is not a de Polignac number, because 21557913 - 2⁹ = 21557401 is a prime.

It is a super-2 number, since 2×21557913² = 929487225831138, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21557917) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34518 + ... + 35136.

It is an arithmetic number, because the mean of its divisors is an integer number (1041600).

Almost surely, 2^21557913 is an apocalyptic number.

It is an amenable number.

21557913 is a deficient number, since it is larger than the sum of its proper divisors (11773287).

21557913 is a wasteful number, since it uses less digits than its factorization.

21557913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 701.

The product of its digits is 9450, while the sum is 33.

The square root of 21557913 is about 4643.0499674244. The cubic root of 21557913 is about 278.3143322713.

The spelling of 21557913 in words is "twenty-one million, five hundred fifty-seven thousand, nine hundred thirteen".