631990821 has 32 divisors (see below), whose sum is σ = 1078990848. Its totient is φ = 319429440.

The previous prime is 631990817. The next prime is 631990847. The reversal of 631990821 is 128099136.

631990821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 631990821 - 2² = 631990817 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 631990821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (631990871) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28425 + ... + 45518.

It is an arithmetic number, because the mean of its divisors is an integer number (33718464).

Almost surely, 2^631990821 is an apocalyptic number.

It is an amenable number.

631990821 is a deficient number, since it is larger than the sum of its proper divisors (447000027).

631990821 is a wasteful number, since it uses less digits than its factorization.

631990821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74001.

The product of its (nonzero) digits is 23328, while the sum is 39.

The square root of 631990821 is about 25139.4276187824. The cubic root of 631990821 is about 858.1639307834.

The spelling of 631990821 in words is "six hundred thirty-one million, nine hundred ninety thousand, eight hundred twenty-one".