621666621 has 12 divisors (see below), whose sum is σ = 898208220. Its totient is φ = 414331200.

The previous prime is 621666611. The next prime is 621666623. The reversal of 621666621 is 126666126.

It is a happy number.

621666621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 317338596 + 304328025 = 17814^2 + 17445^2 .

It is not a de Polignac number, because 621666621 - 2⁹ = 621666109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (621666623) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 37771 + ... + 51671.

It is an arithmetic number, because the mean of its divisors is an integer number (74850685).

Almost surely, 2^621666621 is an apocalyptic number.

It is an amenable number.

621666621 is a deficient number, since it is larger than the sum of its proper divisors (276541599).

621666621 is a wasteful number, since it uses less digits than its factorization.

621666621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18876 (or 18873 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 621666621 is about 24933.2432908356. The cubic root of 621666621 is about 853.4652636017.

It can be divided in two parts, 62166 and 6621, that multiplied together give a triangular number (411601086 = T₂₈₆₉₁).

The spelling of 621666621 in words is "six hundred twenty-one million, six hundred sixty-six thousand, six hundred twenty-one".