81591552 has 108 divisors (see below), whose sum is σ = 268908640. Its totient is φ = 23307264.

The previous prime is 81591541. The next prime is 81591563. The reversal of 81591552 is 25519518.

It is a happy number.

81591552 is a `hidden beast` number, since 8 + 15 + 91 + 552 = 666.

It is an interprime number because it is at equal distance from previous prime (81591541) and next prime (81591563).

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

It is a congruent number.

It is an unprimeable number.

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, 13599 + ... + 18657.

Almost surely, 2^81591552 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81591552, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134454320).

81591552 is an abundant number, since it is smaller than the sum of its proper divisors (187317088).

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

81591552 is a wasteful number, since it uses less digits than its factorization.

81591552 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5088 (or 5071 counting only the distinct ones).

The product of its digits is 18000, while the sum is 36.

The square root of 81591552 is about 9032.8042157461. The cubic root of 81591552 is about 433.7256082312.

The spelling of 81591552 in words is "eighty-one million, five hundred ninety-one thousand, five hundred fifty-two".