621665251 has 4 divisors (see below), whose sum is σ = 623862232. Its totient is φ = 619468272.

The previous prime is 621665173. The next prime is 621665323. The reversal of 621665251 is 152566126.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 621665251 - 2⁹ = 621664739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (621665651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1098066 + ... + 1098631.

It is an arithmetic number, because the mean of its divisors is an integer number (155965558).

Almost surely, 2^621665251 is an apocalyptic number.

621665251 is a deficient number, since it is larger than the sum of its proper divisors (2196981).

621665251 is a wasteful number, since it uses less digits than its factorization.

621665251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2196980.

The product of its digits is 21600, while the sum is 34.

The square root of 621665251 is about 24933.2158174592. The cubic root of 621665251 is about 853.4646366589.

The spelling of 621665251 in words is "six hundred twenty-one million, six hundred sixty-five thousand, two hundred fifty-one".