21611939 has 2 divisors, whose sum is σ = 21611940. Its totient is φ = 21611938.

The previous prime is 21611917. The next prime is 21611957. The reversal of 21611939 is 93911612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21611939 - 2²⁰ = 20563363 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21611999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10805969 + 10805970.

It is an arithmetic number, because the mean of its divisors is an integer number (10805970).

Almost surely, 2^21611939 is an apocalyptic number.

21611939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21611939 is an equidigital number, since it uses as much as digits as its factorization.

21611939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2916, while the sum is 32.

The square root of 21611939 is about 4648.8642699051. The cubic root of 21611939 is about 278.5466316114.

The spelling of 21611939 in words is "twenty-one million, six hundred eleven thousand, nine hundred thirty-nine".