21291265 has 8 divisors (see below), whose sum is σ = 26373888. Its totient is φ = 16483440.

The previous prime is 21291247. The next prime is 21291269. The reversal of 21291265 is 56219212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-21291265 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21291269) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68527 + ... + 68836.

It is an arithmetic number, because the mean of its divisors is an integer number (3296736).

Almost surely, 2^21291265 is an apocalyptic number.

It is an amenable number.

21291265 is a deficient number, since it is larger than the sum of its proper divisors (5082623).

21291265 is a wasteful number, since it uses less digits than its factorization.

21291265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137399.

The product of its digits is 2160, while the sum is 28.

The square root of 21291265 is about 4614.2458755467. The cubic root of 21291265 is about 277.1620863200.

The spelling of 21291265 in words is "twenty-one million, two hundred ninety-one thousand, two hundred sixty-five".