21272665 has 16 divisors (see below), whose sum is σ = 26735616. Its totient is φ = 16228800.

The previous prime is 21272621. The next prime is 21272681. The reversal of 21272665 is 56627212.

It is not a de Polignac number, because 21272665 - 2²³ = 12884057 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10039 + ... + 11971.

It is an arithmetic number, because the mean of its divisors is an integer number (1670976).

Almost surely, 2^21272665 is an apocalyptic number.

It is an amenable number.

21272665 is a deficient number, since it is larger than the sum of its proper divisors (5462951).

21272665 is a wasteful number, since it uses less digits than its factorization.

21272665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2040.

The product of its digits is 10080, while the sum is 31.

The square root of 21272665 is about 4612.2299378934. The cubic root of 21272665 is about 277.0813534196.

Adding to 21272665 its reverse (56627212), we get a palindrome (77899877).

The spelling of 21272665 in words is "twenty-one million, two hundred seventy-two thousand, six hundred sixty-five".