621809525401 has 3 divisors (see below), whose sum is σ = 621810313951. Its totient is φ = 621808736852.

The previous prime is 621809525399. The next prime is 621809525443. The reversal of 621809525401 is 104525908126.

The square root of 621809525401 is 788549.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 430927915401 + 190881610000 = 656451^2 + 436900^2 .

It is not a de Polignac number, because 621809525401 - 2¹ = 621809525399 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (621809525101) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 394275 + ... + 1182823.

Almost surely, 2^621809525401 is an apocalyptic number.

621809525401 is the 788549-th square number.

621809525401 is the 394275-th centered octagonal number.

It is an amenable number.

621809525401 is a deficient number, since it is larger than the sum of its proper divisors (788550).

621809525401 is an frugal number, since it uses more digits than its factorization.

621809525401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1577098 (or 788549 counting only the distinct ones).

The product of its (nonzero) digits is 172800, while the sum is 43.

The spelling of 621809525401 in words is "six hundred twenty-one billion, eight hundred nine million, five hundred twenty-five thousand, four hundred one".