631656901 has 4 divisors (see below), whose sum is σ = 631708204. Its totient is φ = 631605600.

The previous prime is 631656869. The next prime is 631656953. The reversal of 631656901 is 109656136.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 265853025 + 365803876 = 16305^2 + 19126^2 .

It is a 3-Lehmer number, since φ(631656901) divides (631656901-1)³.

It is a cyclic number.

It is not a de Polignac number, because 631656901 - 2⁵ = 631656869 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 (631656001) 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, 5131 + ... + 35911.

It is an arithmetic number, because the mean of its divisors is an integer number (157927051).

Almost surely, 2^631656901 is an apocalyptic number.

631656901 is the 20521-st pentagonal number.

It is an amenable number.

631656901 is a deficient number, since it is larger than the sum of its proper divisors (51303).

631656901 is a wasteful number, since it uses less digits than its factorization.

631656901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51302.

The product of its (nonzero) digits is 29160, while the sum is 37.

The square root of 631656901 is about 25132.7853808526. The cubic root of 631656901 is about 858.0127637232.

The spelling of 631656901 in words is "six hundred thirty-one million, six hundred fifty-six thousand, nine hundred one".