1397906721 has 16 divisors (see below), whose sum is σ = 2076395520. Its totient is φ = 929497680.

The previous prime is 1397906707. The next prime is 1397906791. The reversal of 1397906721 is 1276097931.

It is not a de Polignac number, because 1397906721 - 2⁵ = 1397906689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1397906701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 57250 + ... + 77931.

It is an arithmetic number, because the mean of its divisors is an integer number (129774720).

Almost surely, 2^1397906721 is an apocalyptic number.

It is an amenable number.

1397906721 is a deficient number, since it is larger than the sum of its proper divisors (678488799).

1397906721 is a wasteful number, since it uses less digits than its factorization.

1397906721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135573 (or 135567 counting only the distinct ones).

The product of its (nonzero) digits is 142884, while the sum is 45.

The square root of 1397906721 is about 37388.5907864953. The cubic root of 1397906721 is about 1118.1311096630.

The spelling of 1397906721 in words is "one billion, three hundred ninety-seven million, nine hundred six thousand, seven hundred twenty-one".