21987957 has 8 divisors (see below), whose sum is σ = 29541600. Its totient is φ = 14546480.

The previous prime is 21987947. The next prime is 21987967. The reversal of 21987957 is 75978912.

It is an interprime number because it is at equal distance from previous prime (21987947) and next prime (21987967).

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 21987957 - 2¹² = 21983861 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27582 + ... + 28367.

It is an arithmetic number, because the mean of its divisors is an integer number (3692700).

Almost surely, 2^21987957 is an apocalyptic number.

It is an amenable number.

21987957 is a deficient number, since it is larger than the sum of its proper divisors (7553643).

21987957 is a wasteful number, since it uses less digits than its factorization.

21987957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56083.

The product of its digits is 317520, while the sum is 48.

The square root of 21987957 is about 4689.1317959725. The cubic root of 21987957 is about 280.1527950065.

The spelling of 21987957 in words is "twenty-one million, nine hundred eighty-seven thousand, nine hundred fifty-seven".