21315023 has 2 divisors, whose sum is σ = 21315024. Its totient is φ = 21315022.

The previous prime is 21315013. The next prime is 21315031. The reversal of 21315023 is 32051312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21315023 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21314992 and 21315010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21315013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10657511 + 10657512.

It is an arithmetic number, because the mean of its divisors is an integer number (10657512).

Almost surely, 2^21315023 is an apocalyptic number.

21315023 is a deficient number, since it is larger than the sum of its proper divisors (1).

21315023 is an equidigital number, since it uses as much as digits as its factorization.

21315023 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21315023 is about 4616.8195762884. The cubic root of 21315023 is about 277.2651390527.

Adding to 21315023 its reverse (32051312), we get a palindrome (53366335).

The spelling of 21315023 in words is "twenty-one million, three hundred fifteen thousand, twenty-three".