81121536 has 108 divisors (see below), whose sum is σ = 236517372. Its totient is φ = 26738688.

The previous prime is 81121499. The next prime is 81121541. The reversal of 81121536 is 63512118.

81121536 is a `hidden beast` number, since 8 + 1 + 121 + 536 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 68161536 + 12960000 = 8256^2 + 3600^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 315520 + ... + 315776.

Almost surely, 2^81121536 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 81121536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118258686).

81121536 is an abundant number, since it is smaller than the sum of its proper divisors (155395836).

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

81121536 is a wasteful number, since it uses less digits than its factorization.

81121536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 416 (or 399 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 81121536 is about 9006.7494691481. The cubic root of 81121536 is about 432.8911644851.

The spelling of 81121536 in words is "eighty-one million, one hundred twenty-one thousand, five hundred thirty-six".