631513021 has 4 divisors (see below), whose sum is σ = 631766044. Its totient is φ = 631260000.

The previous prime is 631512953. The next prime is 631513039. The reversal of 631513021 is 120315136.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 231952900 + 399560121 = 15230^2 + 19989^2 .

It is a cyclic number.

It is not a de Polignac number, because 631513021 - 2⁹ = 631512509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 631512983 and 631513001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (631513321) 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, 122730 + ... + 127771.

It is an arithmetic number, because the mean of its divisors is an integer number (157941511).

Almost surely, 2^631513021 is an apocalyptic number.

It is an amenable number.

631513021 is a deficient number, since it is larger than the sum of its proper divisors (253023).

631513021 is a wasteful number, since it uses less digits than its factorization.

631513021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 253022.

The product of its (nonzero) digits is 540, while the sum is 22.

The square root of 631513021 is about 25129.9228212106. The cubic root of 631513021 is about 857.9476121878.

Adding to 631513021 its reverse (120315136), we get a palindrome (751828157).

The spelling of 631513021 in words is "six hundred thirty-one million, five hundred thirteen thousand, twenty-one".