1378699721 has 12 divisors (see below), whose sum is σ = 1608408900. Its totient is φ = 1178341920.

The previous prime is 1378699697. The next prime is 1378699723. The reversal of 1378699721 is 1279968731.

It can be written as a sum of positive squares in 2 ways, for example, as 397444096 + 981255625 = 19936^2 + 31325^2 .

It is not a de Polignac number, because 1378699721 - 2⁶ = 1378699657 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1378699723) 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, 23210 + ... + 57411.

It is an arithmetic number, because the mean of its divisors is an integer number (134034075).

Almost surely, 2^1378699721 is an apocalyptic number.

It is an amenable number.

1378699721 is a deficient number, since it is larger than the sum of its proper divisors (229709179).

1378699721 is an equidigital number, since it uses as much as digits as its factorization.

1378699721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80984 (or 80977 counting only the distinct ones).

The product of its digits is 1143072, while the sum is 53.

The square root of 1378699721 is about 37130.8459505032. The cubic root of 1378699721 is about 1112.9864982606.

The spelling of 1378699721 in words is "one billion, three hundred seventy-eight million, six hundred ninety-nine thousand, seven hundred twenty-one".