620643521 has 4 divisors (see below), whose sum is σ = 620747712. Its totient is φ = 620539332.

The previous prime is 620643511. The next prime is 620643563. The reversal of 620643521 is 125346026.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 620643521 - 2¹⁰ = 620642497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (620643511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42581 + ... + 55266.

It is an arithmetic number, because the mean of its divisors is an integer number (155186928).

Almost surely, 2^620643521 is an apocalyptic number.

It is an amenable number.

620643521 is a deficient number, since it is larger than the sum of its proper divisors (104191).

620643521 is an equidigital number, since it uses as much as digits as its factorization.

620643521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104190.

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 620643521 is about 24912.7180572494. The cubic root of 620643521 is about 852.9968132949.

Adding to 620643521 its reverse (125346026), we get a palindrome (745989547).

The spelling of 620643521 in words is "six hundred twenty million, six hundred forty-three thousand, five hundred twenty-one".