81551886 has 64 divisors (see below), whose sum is σ = 187729920. Its totient is φ = 23425920.

The previous prime is 81551867. The next prime is 81551887. The reversal of 81551886 is 68815518.

It is a happy number.

It is a super-2 number, since 2×81551886² = 13301420220313992, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81551887) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 69541 + ... + 70703.

It is an arithmetic number, because the mean of its divisors is an integer number (2933280).

Almost surely, 2^81551886 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81551886, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93864960).

81551886 is an abundant number, since it is smaller than the sum of its proper divisors (106178034).

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

81551886 is a wasteful number, since it uses less digits than its factorization.

81551886 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1241.

The product of its digits is 76800, while the sum is 42.

The square root of 81551886 is about 9030.6082851600. The cubic root of 81551886 is about 433.6553111303.

The spelling of 81551886 in words is "eighty-one million, five hundred fifty-one thousand, eight hundred eighty-six".