21672391 has 6 divisors (see below), whose sum is σ = 23467920. Its totient is φ = 20005128.

The previous prime is 21672373. The next prime is 21672401. The reversal of 21672391 is 19327612.

It is not a de Polignac number, because 21672391 - 2⁵ = 21672359 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 (21672341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 63951 + ... + 64288.

It is an arithmetic number, because the mean of its divisors is an integer number (3911320).

Almost surely, 2^21672391 is an apocalyptic number.

21672391 is a deficient number, since it is larger than the sum of its proper divisors (1795529).

21672391 is a wasteful number, since it uses less digits than its factorization.

21672391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128265 (or 128252 counting only the distinct ones).

The product of its digits is 4536, while the sum is 31.

The square root of 21672391 is about 4655.3615326847. The cubic root of 21672391 is about 278.8061027793.

The spelling of 21672391 in words is "twenty-one million, six hundred seventy-two thousand, three hundred ninety-one".