81673220 has 24 divisors (see below), whose sum is σ = 177047808. Its totient is φ = 31615200.

The previous prime is 81673181. The next prime is 81673223. The reversal of 81673220 is 2237618.

It is a happy number.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (81673223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65246 + ... + 66485.

It is an arithmetic number, because the mean of its divisors is an integer number (7376992).

Almost surely, 2^81673220 is an apocalyptic number.

It is an amenable number.

81673220 is an abundant number, since it is smaller than the sum of its proper divisors (95374588).

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

81673220 is a wasteful number, since it uses less digits than its factorization.

81673220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131771 (or 131769 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 81673220 is about 9037.3237188893. The cubic root of 81673220 is about 433.8702706398.

The spelling of 81673220 in words is "eighty-one million, six hundred seventy-three thousand, two hundred twenty".