21938913 has 6 divisors (see below), whose sum is σ = 31689554. Its totient is φ = 14625936.

The previous prime is 21938899. The next prime is 21938923. The reversal of 21938913 is 31983912.

It can be written as a sum of positive squares in only one way, i.e., 19607184 + 2331729 = 4428^2 + 1527^2 .

It is not a de Polignac number, because 21938913 - 2⁵ = 21938881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21938923) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1218820 + ... + 1218837.

Almost surely, 2^21938913 is an apocalyptic number.

It is an amenable number.

21938913 is a deficient number, since it is larger than the sum of its proper divisors (9750641).

21938913 is a wasteful number, since it uses less digits than its factorization.

21938913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2437663 (or 2437660 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 21938913 is about 4683.8993370908. The cubic root of 21938913 is about 279.9443469323.

The spelling of 21938913 in words is "twenty-one million, nine hundred thirty-eight thousand, nine hundred thirteen".