81640296 has 24 divisors (see below), whose sum is σ = 221109330. Its totient is φ = 27213408.

The previous prime is 81640291. The next prime is 81640303. The reversal of 81640296 is 69204618.

81640296 is a `hidden beast` number, since 8 + 1 + 640 + 2 + 9 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 80460900 + 1179396 = 8970^2 + 1086^2 .

It is a tau number, because it is divible by the number of its divisors (24).

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 81640296.

It is not an unprimeable number, because it can be changed into a prime (81640291) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 566875 + ... + 567018.

Almost surely, 2^81640296 is an apocalyptic number.

It is an amenable number.

81640296 is an abundant number, since it is smaller than the sum of its proper divisors (139469034).

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

81640296 is a wasteful number, since it uses less digits than its factorization.

81640296 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1133905 (or 1133898 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 81640296 is about 9035.5019783076. The cubic root of 81640296 is about 433.8119624016.

The spelling of 81640296 in words is "eighty-one million, six hundred forty thousand, two hundred ninety-six".