1808920091521 has 9 divisors (see below), whose sum is σ = 1815140273481. Its totient is φ = 1802721166272.

The previous prime is 1808920091507. The next prime is 1808920091543. The reversal of 1808920091521 is 1251900298081.

It is a happy number.

The square root of 1808920091521 is 1344961.

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

It can be written as a sum of positive squares in 4 ways, for example, as 697076377921 + 1111843713600 = 834911^2 + 1054440^2 .

It is not a de Polignac number, because 1808920091521 - 2²⁷ = 1808785873793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1808920091501) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 420970645 + ... + 420974941.

It is an arithmetic number, because the mean of its divisors is an integer number (201682252609).

Almost surely, 2^{1808920091521} is an apocalyptic number.

1808920091521 is the 1344961-st square number.

1808920091521 is the 672481-st centered octagonal number.

It is an amenable number.

1808920091521 is a deficient number, since it is larger than the sum of its proper divisors (6220181960).

1808920091521 is an frugal number, since it uses more digits than its factorization.

1808920091521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9220 (or 4610 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 46.

The spelling of 1808920091521 in words is "one trillion, eight hundred eight billion, nine hundred twenty million, ninety-one thousand, five hundred twenty-one".