81920031 has 8 divisors (see below), whose sum is σ = 111767040. Its totient is φ = 53343192.

The previous prime is 81920023. The next prime is 81920053. The reversal of 81920031 is 13002918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81920031 - 2³ = 81920023 is a prime.

It is a super-2 number, since 2×81920031² = 13421782958081922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81919983 and 81920010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81920021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 317391 + ... + 317648.

It is an arithmetic number, because the mean of its divisors is an integer number (13970880).

Almost surely, 2^81920031 is an apocalyptic number.

81920031 is a deficient number, since it is larger than the sum of its proper divisors (29847009).

81920031 is a wasteful number, since it uses less digits than its factorization.

81920031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 635085.

The product of its (nonzero) digits is 432, while the sum is 24.

The square root of 81920031 is about 9050.9685117119. The cubic root of 81920031 is about 434.3068734383.

Adding to 81920031 its reverse (13002918), we get a palindrome (94922949).

The spelling of 81920031 in words is "eighty-one million, nine hundred twenty thousand, thirty-one".