1397605721 has 2 divisors, whose sum is σ = 1397605722. Its totient is φ = 1397605720.

The previous prime is 1397605697. The next prime is 1397605723. The reversal of 1397605721 is 1275067931.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1205478400 + 192127321 = 34720^2 + 13861^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1397605721 is a prime.

It is a Sophie Germain prime.

Together with 1397605723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1397605723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 698802860 + 698802861.

It is an arithmetic number, because the mean of its divisors is an integer number (698802861).

Almost surely, 2^1397605721 is an apocalyptic number.

It is an amenable number.

1397605721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1397605721 is an equidigital number, since it uses as much as digits as its factorization.

1397605721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 79380, while the sum is 41.

The square root of 1397605721 is about 37384.5652776651. The cubic root of 1397605721 is about 1118.0508511789.

The spelling of 1397605721 in words is "one billion, three hundred ninety-seven million, six hundred five thousand, seven hundred twenty-one".