801990100521 has 9 divisors (see below), whose sum is σ = 1158434025879. Its totient is φ = 534658275936.

The previous prime is 801990100489. The next prime is 801990100531. The reversal of 801990100521 is 125001099108.

The square root of 801990100521 is 895539.

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

It can be written as a sum of positive squares in only one way, i.e., 467138075625 + 334852024896 = 683475^2 + 578664^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 801990100521 - 2⁵ = 801990100489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (801990100531) 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, 2537361 + ... + 2835873.

Almost surely, 2^801990100521 is an apocalyptic number.

801990100521 is the 895539-th square number.

801990100521 is the 447770-th centered octagonal number.

It is an amenable number.

801990100521 is a deficient number, since it is larger than the sum of its proper divisors (356443925358).

801990100521 is an frugal number, since it uses more digits than its factorization.

801990100521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 597032 (or 298516 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 36.

Multiplying 801990100521 by its sum of digits (36), we get a square (28871643618756 = 5373234²).

Adding to 801990100521 its reverse (125001099108), we get a palindrome (926991199629).

The spelling of 801990100521 in words is "eight hundred one billion, nine hundred ninety million, one hundred thousand, five hundred twenty-one".