17621552581 has 2 divisors, whose sum is σ = 17621552582. Its totient is φ = 17621552580.

The previous prime is 17621552579. The next prime is 17621552591. The reversal of 17621552581 is 18525512671.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15154841025 + 2466711556 = 123105^2 + 49666^2 .

It is a cyclic number.

It is not a de Polignac number, because 17621552581 - 2¹ = 17621552579 is a prime.

It is a super-2 number, since 2×17621552581² (a number of 21 digits) contains 22 as substring.

Together with 17621552579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (17621552561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8810776290 + 8810776291.

It is an arithmetic number, because the mean of its divisors is an integer number (8810776291).

Almost surely, 2^17621552581 is an apocalyptic number.

It is an amenable number.

17621552581 is a deficient number, since it is larger than the sum of its proper divisors (1).

17621552581 is an equidigital number, since it uses as much as digits as its factorization.

17621552581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 168000, while the sum is 43.

The spelling of 17621552581 in words is "seventeen billion, six hundred twenty-one million, five hundred fifty-two thousand, five hundred eighty-one".