21672511 has 4 divisors (see below), whose sum is σ = 24768592. Its totient is φ = 18576432.

The previous prime is 21672487. The next prime is 21672517. The reversal of 21672511 is 11527612.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21672511 - 2⁹ = 21671999 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21672517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1548030 + ... + 1548043.

It is an arithmetic number, because the mean of its divisors is an integer number (6192148).

Almost surely, 2^21672511 is an apocalyptic number.

21672511 is a deficient number, since it is larger than the sum of its proper divisors (3096081).

21672511 is an equidigital number, since it uses as much as digits as its factorization.

21672511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3096080.

The product of its digits is 840, while the sum is 25.

The square root of 21672511 is about 4655.3744210321. The cubic root of 21672511 is about 278.8066173613.

It can be divided in two parts, 216 and 72511, that added together give a palindrome (72727).

The spelling of 21672511 in words is "twenty-one million, six hundred seventy-two thousand, five hundred eleven".