81646204644 has 27 divisors (see below), whose sum is σ = 206387795523. Its totient is φ = 27214830072.

The previous prime is 81646204621. The next prime is 81646204681. The reversal of 81646204644 is 44640264618.

The square root of 81646204644 is 285738.

It is a perfect power (a square), and thus also a powerful number.

81646204644 is a `hidden beast` number, since 8 + 16 + 4 + 620 + 4 + 6 + 4 + 4 = 666.

It is a super-2 number, since 2×81646204644² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81646204644.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1690617 + ... + 1738239.

Almost surely, 2^81646204644 is an apocalyptic number.

81646204644 is the 285738-th square number.

It is an amenable number.

81646204644 is an abundant number, since it is smaller than the sum of its proper divisors (124741590879).

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

81646204644 is an frugal number, since it uses more digits than its factorization.

81646204644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95256 (or 47628 counting only the distinct ones).

The product of its (nonzero) digits is 884736, while the sum is 45.

The spelling of 81646204644 in words is "eighty-one billion, six hundred forty-six million, two hundred four thousand, six hundred forty-four".