21659957 has 8 divisors (see below), whose sum is σ = 23667552. Its totient is φ = 19658800.

The previous prime is 21659947. The next prime is 21659969. The reversal of 21659957 is 75995612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21659957 - 2¹⁸ = 21397813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21659947) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7907 + ... + 10287.

It is an arithmetic number, because the mean of its divisors is an integer number (2958444).

Almost surely, 2^21659957 is an apocalyptic number.

It is an amenable number.

21659957 is a deficient number, since it is larger than the sum of its proper divisors (2007595).

21659957 is a wasteful number, since it uses less digits than its factorization.

21659957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3219.

The product of its digits is 170100, while the sum is 44.

The square root of 21659957 is about 4654.0258916340. The cubic root of 21659957 is about 278.7527732033.

The spelling of 21659957 in words is "twenty-one million, six hundred fifty-nine thousand, nine hundred fifty-seven".