15555555 has 12 divisors (see below), whose sum is σ = 26963040. Its totient is φ = 8296272.

The previous prime is 15555541. The next prime is 15555557. The reversal of 15555555 is 55555551.

It is a happy number.

15555555 is a `hidden beast` number, since 1 + 55 + 55 + 555 = 666.

It is not a de Polignac number, because 15555555 - 2⁴ = 15555539 is a prime.

It is a nude number because it is divisible by every one of its digits.

15555555 is a modest number, since divided by 5555 gives 1555 as remainder.

It is a plaindrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15555557) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 172795 + ... + 172884.

It is an arithmetic number, because the mean of its divisors is an integer number (2246920).

Almost surely, 2^15555555 is an apocalyptic number.

15555555 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

15555555 is a deficient number, since it is larger than the sum of its proper divisors (11407485).

15555555 is a wasteful number, since it uses less digits than its factorization.

15555555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345690 (or 345687 counting only the distinct ones).

The product of its digits is 78125, while the sum is 36.

The square root of 15555555 is about 3944.0531183036. The cubic root of 15555555 is about 249.6290766022.

It can be divided in two parts, 15555 and 555, that added together give a triangular number (16110 = T₁₇₉).

The spelling of 15555555 in words is "fifteen million, five hundred fifty-five thousand, five hundred fifty-five".