81997599 has 16 divisors (see below), whose sum is σ = 114580224. Its totient is φ = 52060800.

The previous prime is 81997589. The next prime is 81997607. The reversal of 81997599 is 99579918.

It is not a de Polignac number, because 81997599 - 2⁵ = 81997567 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81997589) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14164 + ... + 19094.

It is an arithmetic number, because the mean of its divisors is an integer number (7161264).

Almost surely, 2^81997599 is an apocalyptic number.

81997599 is a deficient number, since it is larger than the sum of its proper divisors (32582625).

81997599 is a wasteful number, since it uses less digits than its factorization.

81997599 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5198.

The product of its digits is 1837080, while the sum is 57.

The square root of 81997599 is about 9055.2525641199. The cubic root of 81997599 is about 434.4439082509.

The spelling of 81997599 in words is "eighty-one million, nine hundred ninety-seven thousand, five hundred ninety-nine".