23157721 has 2 divisors, whose sum is σ = 23157722. Its totient is φ = 23157720.

The previous prime is 23157703. The next prime is 23157727. The reversal of 23157721 is 12775132.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23088025 + 69696 = 4805^2 + 264^2 .

It is a cyclic number.

It is not a de Polignac number, because 23157721 - 2¹⁹ = 22633433 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 23157721.

It is not a weakly prime, because it can be changed into another prime (23157727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 11578860 + 11578861.

It is an arithmetic number, because the mean of its divisors is an integer number (11578861).

Almost surely, 2^23157721 is an apocalyptic number.

It is an amenable number.

23157721 is a deficient number, since it is larger than the sum of its proper divisors (1).

23157721 is an equidigital number, since it uses as much as digits as its factorization.

23157721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2940, while the sum is 28.

The square root of 23157721 is about 4812.2469803617. The cubic root of 23157721 is about 285.0352721298.

The spelling of 23157721 in words is "twenty-three million, one hundred fifty-seven thousand, seven hundred twenty-one".