21539265 has 32 divisors (see below), whose sum is σ = 38817792. Its totient is φ = 10104000.

The previous prime is 21539263. The next prime is 21539267. The reversal of 21539265 is 56293512.

It is an interprime number because it is at equal distance from previous prime (21539263) and next prime (21539267).

It is not a de Polignac number, because 21539265 - 2¹ = 21539263 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21539263) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3010 + ... + 7220.

It is an arithmetic number, because the mean of its divisors is an integer number (1213056).

Almost surely, 2^21539265 is an apocalyptic number.

It is an amenable number.

21539265 is a deficient number, since it is larger than the sum of its proper divisors (17278527).

21539265 is a wasteful number, since it uses less digits than its factorization.

21539265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4261.

The product of its digits is 16200, while the sum is 33.

The square root of 21539265 is about 4641.0413702099. The cubic root of 21539265 is about 278.2340600781.

The spelling of 21539265 in words is "twenty-one million, five hundred thirty-nine thousand, two hundred sixty-five".