17621572721 has 2 divisors, whose sum is σ = 17621572722. Its totient is φ = 17621572720.

The previous prime is 17621572697. The next prime is 17621572729. The reversal of 17621572721 is 12727512671.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9357853696 + 8263719025 = 96736^2 + 90905^2 .

It is an emirp because it is prime and its reverse (12727512671) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-17621572721 is a prime.

It is a super-2 number, since 2×17621572721² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (17621572729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8810786360 + 8810786361.

It is an arithmetic number, because the mean of its divisors is an integer number (8810786361).

Almost surely, 2^17621572721 is an apocalyptic number.

It is an amenable number.

17621572721 is a deficient number, since it is larger than the sum of its proper divisors (1).

17621572721 is an equidigital number, since it uses as much as digits as its factorization.

17621572721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82320, while the sum is 41.

The spelling of 17621572721 in words is "seventeen billion, six hundred twenty-one million, five hundred seventy-two thousand, seven hundred twenty-one".