21858957 has 16 divisors (see below), whose sum is σ = 34289280. Its totient is φ = 13715136.

The previous prime is 21858931. The next prime is 21858979. The reversal of 21858957 is 75985812.

It is a happy number.

21858957 is a `hidden beast` number, since 2 + 18 + 589 + 57 = 666.

It is not a de Polignac number, because 21858957 - 2¹⁰ = 21857933 is a prime.

It is a super-3 number, since 3×21858957³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21858997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23353 + ... + 24270.

It is an arithmetic number, because the mean of its divisors is an integer number (2143080).

Almost surely, 2^21858957 is an apocalyptic number.

21858957 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21858957 is a deficient number, since it is larger than the sum of its proper divisors (12430323).

21858957 is a wasteful number, since it uses less digits than its factorization.

21858957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47649 (or 47643 counting only the distinct ones).

The product of its digits is 201600, while the sum is 45.

The square root of 21858957 is about 4675.3563500550. The cubic root of 21858957 is about 279.6038487930.

The spelling of 21858957 in words is "twenty-one million, eight hundred fifty-eight thousand, nine hundred fifty-seven".