81581807064 has 32 divisors (see below), whose sum is σ = 205973875440. Its totient is φ = 26924688000.

The previous prime is 81581807051. The next prime is 81581807071. The reversal of 81581807064 is 46070818518.

It is a happy number.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16825507 + ... + 16830354.

Almost surely, 2^81581807064 is an apocalyptic number.

It is an amenable number.

81581807064 is an abundant number, since it is smaller than the sum of its proper divisors (124392068376).

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

81581807064 is a wasteful number, since it uses less digits than its factorization.

81581807064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33655971 (or 33655967 counting only the distinct ones).

The product of its (nonzero) digits is 430080, while the sum is 48.

The spelling of 81581807064 in words is "eighty-one billion, five hundred eighty-one million, eight hundred seven thousand, sixty-four".