81621719793 has 48 divisors (see below), whose sum is σ = 126657929216. Its totient is φ = 52471728720.

The previous prime is 81621719783. The next prime is 81621719801. The reversal of 81621719793 is 39791712618.

It is a happy number.

81621719793 is a `hidden beast` number, since 8 + 1 + 621 + 7 + 1 + 9 + 7 + 9 + 3 = 666.

It is not a de Polignac number, because 81621719793 - 2¹⁸ = 81621457649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81621719713) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2112696 + ... + 2150982.

Almost surely, 2^81621719793 is an apocalyptic number.

It is an amenable number.

81621719793 is a deficient number, since it is larger than the sum of its proper divisors (45036209423).

81621719793 is a wasteful number, since it uses less digits than its factorization.

81621719793 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38616 (or 38604 counting only the distinct ones).

The product of its digits is 1143072, while the sum is 54.

The spelling of 81621719793 in words is "eighty-one billion, six hundred twenty-one million, seven hundred nineteen thousand, seven hundred ninety-three".