17947660721 has 2 divisors, whose sum is σ = 17947660722. Its totient is φ = 17947660720.

The previous prime is 17947660681. The next prime is 17947660727. The reversal of 17947660721 is 12706674971.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15301690000 + 2645970721 = 123700^2 + 51439^2 .

It is a cyclic number.

It is not a de Polignac number, because 17947660721 - 2²² = 17943466417 is a prime.

It is a super-2 number, since 2×17947660721² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 17947660721.

It is not a weakly prime, because it can be changed into another prime (17947660727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8973830360 + 8973830361.

It is an arithmetic number, because the mean of its divisors is an integer number (8973830361).

Almost surely, 2^17947660721 is an apocalyptic number.

It is an amenable number.

17947660721 is a deficient number, since it is larger than the sum of its proper divisors (1).

17947660721 is an equidigital number, since it uses as much as digits as its factorization.

17947660721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 889056, while the sum is 50.

The spelling of 17947660721 in words is "seventeen billion, nine hundred forty-seven million, six hundred sixty thousand, seven hundred twenty-one".