81907780 has 24 divisors (see below), whose sum is σ = 172343808. Its totient is φ = 32698848.

The previous prime is 81907747. The next prime is 81907781. The reversal of 81907780 is 8770918.

It is not an unprimeable number, because it can be changed into a prime (81907781) 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, 7197 + ... + 14683.

It is an arithmetic number, because the mean of its divisors is an integer number (7180992).

Almost surely, 2^81907780 is an apocalyptic number.

It is an amenable number.

81907780 is an abundant number, since it is smaller than the sum of its proper divisors (90436028).

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

81907780 is a wasteful number, since it uses less digits than its factorization.

81907780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8043 (or 8041 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 40.

The square root of 81907780 is about 9050.2917080059. The cubic root of 81907780 is about 434.2852224099.

The spelling of 81907780 in words is "eighty-one million, nine hundred seven thousand, seven hundred eighty".