1381238721 has 12 divisors (see below), whose sum is σ = 2003404260. Its totient is φ = 917003520.

The previous prime is 1381238713. The next prime is 1381238741. The reversal of 1381238721 is 1278321831.

It can be written as a sum of positive squares in 2 ways, for example, as 1252098225 + 129140496 = 35385^2 + 11364^2 .

It is not a de Polignac number, because 1381238721 - 2³ = 1381238713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1381238741) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 316236 + ... + 320573.

It is an arithmetic number, because the mean of its divisors is an integer number (166950355).

Almost surely, 2^1381238721 is an apocalyptic number.

It is an amenable number.

1381238721 is a deficient number, since it is larger than the sum of its proper divisors (622165539).

1381238721 is a wasteful number, since it uses less digits than its factorization.

1381238721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 637056 (or 637053 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 1381238721 is about 37165.0201264576. The cubic root of 1381238721 is about 1113.6693009886.

The spelling of 1381238721 in words is "one billion, three hundred eighty-one million, two hundred thirty-eight thousand, seven hundred twenty-one".