656747921 has 2 divisors, whose sum is σ = 656747922. Its totient is φ = 656747920.

The previous prime is 656747849. The next prime is 656747929. The reversal of 656747921 is 129747656.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 652291600 + 4456321 = 25540^2 + 2111^2 .

It is a cyclic number.

It is not a de Polignac number, because 656747921 - 2²² = 652553617 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (656747929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328373960 + 328373961.

It is an arithmetic number, because the mean of its divisors is an integer number (328373961).

Almost surely, 2^656747921 is an apocalyptic number.

It is an amenable number.

656747921 is a deficient number, since it is larger than the sum of its proper divisors (1).

656747921 is an equidigital number, since it uses as much as digits as its factorization.

656747921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 635040, while the sum is 47.

The square root of 656747921 is about 25627.0934949713. The cubic root of 656747921 is about 869.2263880928.

The spelling of 656747921 in words is "six hundred fifty-six million, seven hundred forty-seven thousand, nine hundred twenty-one".