81538173 has 24 divisors (see below), whose sum is σ = 119721888. Its totient is φ = 53469792.

The previous prime is 81538141. The next prime is 81538181. The reversal of 81538173 is 37183518.

81538173 = T₄₂ + T₄₃ + ... + T₇₈₇.

It is not a de Polignac number, because 81538173 - 2⁵ = 81538141 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81538123) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 218415 + ... + 218787.

It is an arithmetic number, because the mean of its divisors is an integer number (4988412).

Almost surely, 2^81538173 is an apocalyptic number.

It is an amenable number.

81538173 is a deficient number, since it is larger than the sum of its proper divisors (38183715).

81538173 is a wasteful number, since it uses less digits than its factorization.

81538173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 713 (or 710 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 81538173 is about 9029.8490020598. The cubic root of 81538173 is about 433.6310032983.

The spelling of 81538173 in words is "eighty-one million, five hundred thirty-eight thousand, one hundred seventy-three".