631 has 2 divisors, whose sum is σ = 632. Its totient is φ = 630.

The previous prime is 619. The next prime is 641. The reversal of 631 is 136.

631 = T_{19} + T_{20} +
T_{21}.

631 is an esthetic number in base 3, because in such base its adjacent digits differ by 1.

It is an a-pointer prime, because the next prime (641) can be obtained adding 631 to its sum of digits (10).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 631 - 2^{5} = 599 is a prime.

It is a super-2 number, since 2×631^{2} = 796322, which contains 22 as substring.

It is a Chen prime.

It is a pancake number, because a pancake can be divided into 631 parts by 35 straight cuts.

631 is a lucky number.

It is a plaindrome in base 8, base 12 and base 16.

It is a nialpdrome in base 9, base 10 and base 14.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 315 + 316.

It is an arithmetic number, because the mean of its divisors is an integer number (316).

631 is the 21-st centered triangular number and also the 15-th hex number.

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

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

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

The product of its digits is 18, while the sum is 10.

The square root of 631 is about 25.1197133742. The cubic root of 631 is about 8.5771522617.

Adding to 631 its reverse (136), we get a palindrome (767).

It can be divided in two parts, 63 and 1, that added together give a 6-th power (64 = 2^{6}).

The spelling of 631 in words is "six hundred thirty-one", and thus it is an aban number.

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