81559040 has 40 divisors (see below), whose sum is σ = 195556680. Its totient is φ = 32622592.

The previous prime is 81558973. The next prime is 81559043. The reversal of 81559040 is 4095518.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 81558988 and 81559006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81559043) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13370 + ... + 18489.

It is an arithmetic number, because the mean of its divisors is an integer number (4888917).

Almost surely, 2^81559040 is an apocalyptic number.

81559040 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81559040 is an abundant number, since it is smaller than the sum of its proper divisors (113997640).

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

81559040 is an equidigital number, since it uses as much as digits as its factorization.

81559040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31882 (or 31866 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 32.

The square root of 81559040 is about 9031.0043738224. The cubic root of 81559040 is about 433.6679913169.

The spelling of 81559040 in words is "eighty-one million, five hundred fifty-nine thousand, forty".