21618953 has 2 divisors, whose sum is σ = 21618954. Its totient is φ = 21618952.

The previous prime is 21618943. The next prime is 21618959. The reversal of 21618953 is 35981612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21557449 + 61504 = 4643^2 + 248^2 .

It is a cyclic number.

It is not a de Polignac number, because 21618953 - 2⁶ = 21618889 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21618959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10809476 + 10809477.

It is an arithmetic number, because the mean of its divisors is an integer number (10809477).

Almost surely, 2^21618953 is an apocalyptic number.

It is an amenable number.

21618953 is a deficient number, since it is larger than the sum of its proper divisors (1).

21618953 is an equidigital number, since it uses as much as digits as its factorization.

21618953 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 35.

The square root of 21618953 is about 4649.6185865079. The cubic root of 21618953 is about 278.5767617901.

The spelling of 21618953 in words is "twenty-one million, six hundred eighteen thousand, nine hundred fifty-three".