81764267621 has 4 divisors (see below), whose sum is σ = 81777455232. Its totient is φ = 81751080012.

The previous prime is 81764267597. The next prime is 81764267647. The reversal of 81764267621 is 12676246718.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81764267621 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81764267621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81764207621) 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, 6584501 + ... + 6596906.

It is an arithmetic number, because the mean of its divisors is an integer number (20444363808).

Almost surely, 2^81764267621 is an apocalyptic number.

It is an amenable number.

81764267621 is a deficient number, since it is larger than the sum of its proper divisors (13187611).

81764267621 is a wasteful number, since it uses less digits than its factorization.

81764267621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13187610.

The product of its digits is 1354752, while the sum is 50.

The spelling of 81764267621 in words is "eighty-one billion, seven hundred sixty-four million, two hundred sixty-seven thousand, six hundred twenty-one".