81640216 has 16 divisors (see below), whose sum is σ = 174943440. Its totient is φ = 34988640.

The previous prime is 81640213. The next prime is 81640243. The reversal of 81640216 is 61204618.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81640213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 728875 + ... + 728986.

It is an arithmetic number, because the mean of its divisors is an integer number (10933965).

Almost surely, 2^81640216 is an apocalyptic number.

It is an amenable number.

81640216 is an abundant number, since it is smaller than the sum of its proper divisors (93303224).

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

81640216 is a wasteful number, since it uses less digits than its factorization.

81640216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1457874 (or 1457870 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 81640216 is about 9035.4975513250. The cubic root of 81640216 is about 433.8118207029.

The spelling of 81640216 in words is "eighty-one million, six hundred forty thousand, two hundred sixteen".