172991538 has 20 divisors (see below), whose sum is σ = 387629550. Its totient is φ = 57663792.

The previous prime is 172991527. The next prime is 172991543. The reversal of 172991538 is 835199271.

172991538 is a `hidden beast` number, since 1 + 7 + 29 + 91 + 538 = 666.

It can be written as a sum of positive squares in only one way, i.e., 161722089 + 11269449 = 12717^2 + 3357^2 .

It is a junction number, because it is equal to n+sod(n) for n = 172991493 and 172991502.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 533763 + ... + 534086.

Almost surely, 2^172991538 is an apocalyptic number.

172991538 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

172991538 is an abundant number, since it is smaller than the sum of its proper divisors (214638012).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

172991538 is a wasteful number, since it uses less digits than its factorization.

172991538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1067863 (or 1067854 counting only the distinct ones).

The product of its digits is 136080, while the sum is 45.

The square root of 172991538 is about 13152.6247570589. The cubic root of 172991538 is about 557.1963804877.

The spelling of 172991538 in words is "one hundred seventy-two million, nine hundred ninety-one thousand, five hundred thirty-eight".