21947913 has 24 divisors (see below), whose sum is σ = 34474440. Its totient is φ = 13374720.

The previous prime is 21947903. The next prime is 21947921. The reversal of 21947913 is 31974912.

It can be written as a sum of positive squares in 4 ways, for example, as 3697929 + 18249984 = 1923^2 + 4272^2 .

It is not a de Polignac number, because 21947913 - 2⁴ = 21947897 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21947903) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11893 + ... + 13613.

It is an arithmetic number, because the mean of its divisors is an integer number (1436435).

Almost surely, 2^21947913 is an apocalyptic number.

It is an amenable number.

21947913 is a deficient number, since it is larger than the sum of its proper divisors (12526527).

21947913 is a wasteful number, since it uses less digits than its factorization.

21947913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1849 (or 1846 counting only the distinct ones).

The product of its digits is 13608, while the sum is 36.

The square root of 21947913 is about 4684.8599765628. The cubic root of 21947913 is about 279.9826222208.

The spelling of 21947913 in words is "twenty-one million, nine hundred forty-seven thousand, nine hundred thirteen".