81431760 has 80 divisors (see below), whose sum is σ = 254358720. Its totient is φ = 21550080.

The previous prime is 81431759. The next prime is 81431789. The reversal of 81431760 is 6713418.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×81431760² = 13262263073395200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32140 + ... + 34580.

It is an arithmetic number, because the mean of its divisors is an integer number (3179484).

Almost surely, 2^81431760 is an apocalyptic number.

81431760 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81431760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (127179360).

81431760 is an abundant number, since it is smaller than the sum of its proper divisors (172926960).

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

81431760 is a wasteful number, since it uses less digits than its factorization.

81431760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2596 (or 2590 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 81431760 is about 9023.9547871208. The cubic root of 81431760 is about 433.4422816133.

The spelling of 81431760 in words is "eighty-one million, four hundred thirty-one thousand, seven hundred sixty".