81561456 has 60 divisors (see below), whose sum is σ = 236141880. Its totient is φ = 26248320.

The previous prime is 81561421. The next prime is 81561457. The reversal of 81561456 is 65416518.

It is a super-2 number, since 2×81561456² = 13304542209679872, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 81561456.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81561457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5590 + ... + 13941.

It is an arithmetic number, because the mean of its divisors is an integer number (3935698).

Almost surely, 2^81561456 is an apocalyptic number.

It is an amenable number.

81561456 is an abundant number, since it is smaller than the sum of its proper divisors (154580424).

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

81561456 is a wasteful number, since it uses less digits than its factorization.

81561456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19574 (or 19565 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

The square root of 81561456 is about 9031.1381342553. The cubic root of 81561456 is about 433.6722734153.

The spelling of 81561456 in words is "eighty-one million, five hundred sixty-one thousand, four hundred fifty-six".