21623663 has 2 divisors, whose sum is σ = 21623664. Its totient is φ = 21623662.

The previous prime is 21623639. The next prime is 21623681. The reversal of 21623663 is 36632612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21623663 - 2⁶ = 21623599 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21623603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10811831 + 10811832.

It is an arithmetic number, because the mean of its divisors is an integer number (10811832).

Almost surely, 2^21623663 is an apocalyptic number.

21623663 is a deficient number, since it is larger than the sum of its proper divisors (1).

21623663 is an equidigital number, since it uses as much as digits as its factorization.

21623663 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 29.

The square root of 21623663 is about 4650.1250520819. The cubic root of 21623663 is about 278.5969909732.

The spelling of 21623663 in words is "twenty-one million, six hundred twenty-three thousand, six hundred sixty-three".