21811265 has 16 divisors (see below), whose sum is σ = 29998080. Its totient is φ = 14913600.

The previous prime is 21811261. The next prime is 21811351. The reversal of 21811265 is 56211812.

It is not a de Polignac number, because 21811265 - 2² = 21811261 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21811261) 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, 16115 + ... + 17415.

It is an arithmetic number, because the mean of its divisors is an integer number (1874880).

Almost surely, 2^21811265 is an apocalyptic number.

It is an amenable number.

21811265 is a deficient number, since it is larger than the sum of its proper divisors (8186815).

21811265 is a wasteful number, since it uses less digits than its factorization.

21811265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1792.

The product of its digits is 960, while the sum is 26.

The square root of 21811265 is about 4670.2532051271. The cubic root of 21811265 is about 279.4003536223.

The spelling of 21811265 in words is "twenty-one million, eight hundred eleven thousand, two hundred sixty-five".