15551660581 has 2 divisors, whose sum is σ = 15551660582. Its totient is φ = 15551660580.

The previous prime is 15551660563. The next prime is 15551660623. The reversal of 15551660581 is 18506615551.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10051065025 + 5500595556 = 100255^2 + 74166^2 .

It is a cyclic number.

It is not a de Polignac number, because 15551660581 - 2⁵ = 15551660549 is a prime.

It is a super-2 number, since 2×15551660581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15551660881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7775830290 + 7775830291.

It is an arithmetic number, because the mean of its divisors is an integer number (7775830291).

Almost surely, 2^15551660581 is an apocalyptic number.

It is an amenable number.

15551660581 is a deficient number, since it is larger than the sum of its proper divisors (1).

15551660581 is an equidigital number, since it uses as much as digits as its factorization.

15551660581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 180000, while the sum is 43.

The spelling of 15551660581 in words is "fifteen billion, five hundred fifty-one million, six hundred sixty thousand, five hundred eighty-one".