631881881921 has 2 divisors, whose sum is σ = 631881881922. Its totient is φ = 631881881920.

The previous prime is 631881881887. The next prime is 631881881951. The reversal of 631881881921 is 129188188136.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 600291796225 + 31590085696 = 774785^2 + 177736^2 .

It is a cyclic number.

It is not a de Polignac number, because 631881881921 - 2¹⁸ = 631881619777 is a prime.

It is not a weakly prime, because it can be changed into another prime (631881881951) 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 as a sum of consecutive naturals, namely, 315940940960 + 315940940961.

It is an arithmetic number, because the mean of its divisors is an integer number (315940940961).

Almost surely, 2^631881881921 is an apocalyptic number.

It is an amenable number.

631881881921 is a deficient number, since it is larger than the sum of its proper divisors (1).

631881881921 is an equidigital number, since it uses as much as digits as its factorization.

631881881921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1327104, while the sum is 56.

The spelling of 631881881921 in words is "six hundred thirty-one billion, eight hundred eighty-one million, eight hundred eighty-one thousand, nine hundred twenty-one".