81564560 has 80 divisors (see below), whose sum is σ = 236449152. Its totient is φ = 25420800.

The previous prime is 81564551. The next prime is 81564569. The reversal of 81564560 is 6546518.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81564551) and next prime (81564569).

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

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 81564560.

It is not an unprimeable number, because it can be changed into a prime (81564569) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 461 + ... + 12780.

Almost surely, 2^81564560 is an apocalyptic number.

81564560 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 81564560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118224576).

81564560 is an abundant number, since it is smaller than the sum of its proper divisors (154884592).

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

81564560 is a wasteful number, since it uses less digits than its factorization.

81564560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13272 (or 13266 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 35.

The square root of 81564560 is about 9031.3099824998. The cubic root of 81564560 is about 433.6777747952.

The spelling of 81564560 in words is "eighty-one million, five hundred sixty-four thousand, five hundred sixty".