21881913 has 4 divisors (see below), whose sum is σ = 29175888. Its totient is φ = 14587940.

The previous prime is 21881903. The next prime is 21881917. The reversal of 21881913 is 31918812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21881913 - 2¹³ = 21873721 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21881917) 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 3 ways as a sum of consecutive naturals, for example, 3646983 + ... + 3646988.

It is an arithmetic number, because the mean of its divisors is an integer number (7293972).

Almost surely, 2^21881913 is an apocalyptic number.

It is an amenable number.

21881913 is a deficient number, since it is larger than the sum of its proper divisors (7293975).

21881913 is an equidigital number, since it uses as much as digits as its factorization.

21881913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7293974.

The product of its digits is 3456, while the sum is 33.

The square root of 21881913 is about 4677.8107058751. The cubic root of 21881913 is about 279.7016933571.

The spelling of 21881913 in words is "twenty-one million, eight hundred eighty-one thousand, nine hundred thirteen".