21264557 has 4 divisors (see below), whose sum is σ = 21343296. Its totient is φ = 21185820.

The previous prime is 21264541. The next prime is 21264559. The reversal of 21264557 is 75546212.

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 not a de Polignac number, because 21264557 - 2⁴ = 21264541 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264559) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38963 + ... + 39504.

It is an arithmetic number, because the mean of its divisors is an integer number (5335824).

Almost surely, 2^21264557 is an apocalyptic number.

It is an amenable number.

21264557 is a deficient number, since it is larger than the sum of its proper divisors (78739).

21264557 is an equidigital number, since it uses as much as digits as its factorization.

21264557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78738.

The product of its digits is 16800, while the sum is 32.

The square root of 21264557 is about 4611.3508866708. The cubic root of 21264557 is about 277.0461460913.

The spelling of 21264557 in words is "twenty-one million, two hundred sixty-four thousand, five hundred fifty-seven".