126631381869721 has 3 divisors (see below), whose sum is σ = 126631393122783. Its totient is φ = 126631370616660.

The previous prime is 126631381869677. The next prime is 126631381869757. The reversal of 126631381869721 is 127968183136621.

The square root of 126631381869721 is 11253061.

It is a perfect power (a square), and thus also a powerful number.

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 only one way, i.e., 97455179619721 + 29176202250000 = 9871939^2 + 5401500^2 .

It is not a de Polignac number, because 126631381869721 - 2²³ = 126631373481113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (126631381869221) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 5626531 + ... + 16879591.

It is an arithmetic number, because the mean of its divisors is an integer number (42210464374261).

Almost surely, 2^{126631381869721} is an apocalyptic number.

126631381869721 is the 11253061-st square number.

126631381869721 is the 5626531-st centered octagonal number.

It is an amenable number.

126631381869721 is a deficient number, since it is larger than the sum of its proper divisors (11253062).

126631381869721 is an frugal number, since it uses more digits than its factorization.

126631381869721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22506122 (or 11253061 counting only the distinct ones).

The product of its digits is 31352832, while the sum is 64.

The spelling of 126631381869721 in words is "one hundred twenty-six trillion, six hundred thirty-one billion, three hundred eighty-one million, eight hundred sixty-nine thousand, seven hundred twenty-one".