21264565 has 16 divisors (see below), whose sum is σ = 29237760. Its totient is φ = 14544000.

The previous prime is 21264563. The next prime is 21264577. The reversal of 21264565 is 56546212.

21264565 = 397² + 398² + ... + 501².

It is not a de Polignac number, because 21264565 - 2¹ = 21264563 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264563) 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, 25881 + ... + 26689.

It is an arithmetic number, because the mean of its divisors is an integer number (1827360).

Almost surely, 2^21264565 is an apocalyptic number.

It is an amenable number.

21264565 is a deficient number, since it is larger than the sum of its proper divisors (7973195).

21264565 is an equidigital number, since it uses as much as digits as its factorization.

21264565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1572.

The product of its digits is 14400, while the sum is 31.

The square root of 21264565 is about 4611.3517540955. The cubic root of 21264565 is about 277.0461808341.

The spelling of 21264565 in words is "twenty-one million, two hundred sixty-four thousand, five hundred sixty-five".