1581016644 has 75 divisors (see below), whose sum is σ = 4222939567. Its totient is φ = 515792664.

The previous prime is 1581016639. The next prime is 1581016663. The reversal of 1581016644 is 4466101851.

The square root of 1581016644 is 39762.

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

1581016644 is a `hidden beast` number, since 1 + 5 + 8 + 1 + 0 + 1 + 6 + 644 = 666.

It is an ABA number since it can be written as A⋅B^A, here for A=4, B=141.

It is a super-2 number, since 2×1581016644² = 4999227257210045472, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1581016599 and 1581016608.

It is an unprimeable number.

It is a polite number, since it can be written in 24 ways as a sum of consecutive naturals, for example, 33638629 + ... + 33638675.

Almost surely, 2^1581016644 is an apocalyptic number.

1581016644 is the 39762-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1581016644

1581016644 is an abundant number, since it is smaller than the sum of its proper divisors (2641922923).

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

1581016644 is an frugal number, since it uses more digits than its factorization.

1581016644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204 (or 52 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The cubic root of 1581016644 is about 1164.9630408188.

Multiplying 1581016644 by its sum of digits (36), we get a square (56916599184 = 238572²).

1581016644 divided by its sum of digits (36) gives a square (43917129 = 6627²).

The spelling of 1581016644 in words is "one billion, five hundred eighty-one million, sixteen thousand, six hundred forty-four".