21487957 has 4 divisors (see below), whose sum is σ = 22422240. Its totient is φ = 20553676.

The previous prime is 21487951. The next prime is 21487981. The reversal of 21487957 is 75978412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21487957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21487951) 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 3 ways as a sum of consecutive naturals, for example, 467107 + ... + 467152.

It is an arithmetic number, because the mean of its divisors is an integer number (5605560).

Almost surely, 2^21487957 is an apocalyptic number.

It is an amenable number.

21487957 is a deficient number, since it is larger than the sum of its proper divisors (934283).

21487957 is an equidigital number, since it uses as much as digits as its factorization.

21487957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 934282.

The product of its digits is 141120, while the sum is 43.

The square root of 21487957 is about 4635.5104357557. The cubic root of 21487957 is about 278.0129602501.

The spelling of 21487957 in words is "twenty-one million, four hundred eighty-seven thousand, nine hundred fifty-seven".