81923517 has 12 divisors (see below), whose sum is σ = 127436764. Its totient is φ = 50414400.

The previous prime is 81923507. The next prime is 81923537. The reversal of 81923517 is 71532918.

It can be written as a sum of positive squares in 2 ways, for example, as 12467961 + 69455556 = 3531^2 + 8334^2 .

It is not a de Polignac number, because 81923517 - 2¹² = 81919421 is a prime.

It is a super-2 number, since 2×81923517² = 13422925275298578, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81923507) 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, 349984 + ... + 350217.

Almost surely, 2^81923517 is an apocalyptic number.

It is an amenable number.

81923517 is a deficient number, since it is larger than the sum of its proper divisors (45513247).

81923517 is a wasteful number, since it uses less digits than its factorization.

81923517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 700220 (or 700217 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 81923517 is about 9051.1610857392. The cubic root of 81923517 is about 434.3130338050.

It can be divided in two parts, 819 and 23517, that added together give a square (24336 = 156²).

The spelling of 81923517 in words is "eighty-one million, nine hundred twenty-three thousand, five hundred seventeen".