21972865 has 8 divisors (see below), whose sum is σ = 27276840. Its totient is φ = 16972032.

The previous prime is 21972833. The next prime is 21972869. The reversal of 21972865 is 56827912.

It can be written as a sum of positive squares in 4 ways, for example, as 3370896 + 18601969 = 1836^2 + 4313^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21972865 - 2⁵ = 21972833 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21972869) 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, 75624 + ... + 75913.

It is an arithmetic number, because the mean of its divisors is an integer number (3409605).

Almost surely, 2^21972865 is an apocalyptic number.

It is an amenable number.

21972865 is a deficient number, since it is larger than the sum of its proper divisors (5303975).

21972865 is a wasteful number, since it uses less digits than its factorization.

21972865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151571.

The product of its digits is 60480, while the sum is 40.

The square root of 21972865 is about 4687.5222666138. The cubic root of 21972865 is about 280.0886836432.

The spelling of 21972865 in words is "twenty-one million, nine hundred seventy-two thousand, eight hundred sixty-five".