21579957 has 48 divisors (see below), whose sum is σ = 38009088. Its totient is φ = 11531520.

The previous prime is 21579947. The next prime is 21579959. The reversal of 21579957 is 75997512.

21579957 is a `hidden beast` number, since 21 + 579 + 9 + 57 = 666.

It is not a de Polignac number, because 21579957 - 2¹² = 21575861 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21579959) 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 47 ways as a sum of consecutive naturals, for example, 76657 + ... + 76937.

It is an arithmetic number, because the mean of its divisors is an integer number (791856).

Almost surely, 2^21579957 is an apocalyptic number.

It is an amenable number.

21579957 is a deficient number, since it is larger than the sum of its proper divisors (16429131).

21579957 is a wasteful number, since it uses less digits than its factorization.

21579957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 370 (or 367 counting only the distinct ones).

The product of its digits is 198450, while the sum is 45.

The square root of 21579957 is about 4645.4232315258. The cubic root of 21579957 is about 278.4091632066.

The spelling of 21579957 in words is "twenty-one million, five hundred seventy-nine thousand, nine hundred fifty-seven".