621631 has 2 divisors, whose sum is σ = 621632. Its totient is φ = 621630.

The previous prime is 621629. The next prime is 621641. The reversal of 621631 is 136126.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 621631 - 2¹ = 621629 is a prime.

It is a super-2 number, since 2×621631² = 772850200322, which contains 22 as substring.

Together with 621629, it forms a pair of twin primes.

It is equal to p₅₀₇₃₄ and since 621631 and 50734 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 621599 and 621608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (621611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310815 + 310816.

It is an arithmetic number, because the mean of its divisors is an integer number (310816).

2⁶²¹⁶³¹ is an apocalyptic number.

621631 is a deficient number, since it is larger than the sum of its proper divisors (1).

621631 is an equidigital number, since it uses as much as digits as its factorization.

621631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216, while the sum is 19.

The square root of 621631 is about 788.4357932007. The cubic root of 621631 is about 85.3448962331.

Adding to 621631 its reverse (136126), we get a palindrome (757757).

The spelling of 621631 in words is "six hundred twenty-one thousand, six hundred thirty-one".