621621661 has 4 divisors (see below), whose sum is σ = 621672832. Its totient is φ = 621570492.

The previous prime is 621621653. The next prime is 621621731. The reversal of 621621661 is 166126126.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 621621661 - 2³ = 621621653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (621621601) 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, 4180 + ... + 35506.

It is an arithmetic number, because the mean of its divisors is an integer number (155418208).

Almost surely, 2^621621661 is an apocalyptic number.

It is an amenable number.

621621661 is a deficient number, since it is larger than the sum of its proper divisors (51171).

621621661 is a wasteful number, since it uses less digits than its factorization.

621621661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51170.

The product of its digits is 5184, while the sum is 31.

The square root of 621621661 is about 24932.3416669995. The cubic root of 621621661 is about 853.4446884135. Note that the first 3 decimals are identical.

Adding to 621621661 its reverse (166126126), we get a palindrome (787747787).

The spelling of 621621661 in words is "six hundred twenty-one million, six hundred twenty-one thousand, six hundred sixty-one".