39964657721 has 2 divisors, whose sum is σ = 39964657722. Its totient is φ = 39964657720.

The previous prime is 39964657693. The next prime is 39964657727. The reversal of 39964657721 is 12775646993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 38078058496 + 1886599225 = 195136^2 + 43435^2 .

It is a cyclic number.

It is not a de Polignac number, because 39964657721 - 2¹⁸ = 39964395577 is a prime.

It is not a weakly prime, because it can be changed into another prime (39964657727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19982328860 + 19982328861.

It is an arithmetic number, because the mean of its divisors is an integer number (19982328861).

Almost surely, 2^39964657721 is an apocalyptic number.

It is an amenable number.

39964657721 is a deficient number, since it is larger than the sum of its proper divisors (1).

39964657721 is an equidigital number, since it uses as much as digits as its factorization.

39964657721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17146080, while the sum is 59.

The spelling of 39964657721 in words is "thirty-nine billion, nine hundred sixty-four million, six hundred fifty-seven thousand, seven hundred twenty-one".