1897312721 has 2 divisors, whose sum is σ = 1897312722. Its totient is φ = 1897312720.

The previous prime is 1897312691. The next prime is 1897312723. The reversal of 1897312721 is 1272137981.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1187836225 + 709476496 = 34465^2 + 26636^2 .

It is a cyclic number.

It is not a de Polignac number, because 1897312721 - 2¹⁴ = 1897296337 is a prime.

It is a super-2 number, since 2×1897312721² = 7199591122536847682, which contains 22 as substring.

Together with 1897312723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1897312723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 948656360 + 948656361.

It is an arithmetic number, because the mean of its divisors is an integer number (948656361).

Almost surely, 2^1897312721 is an apocalyptic number.

It is an amenable number.

1897312721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1897312721 is an equidigital number, since it uses as much as digits as its factorization.

1897312721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 42336, while the sum is 41.

The square root of 1897312721 is about 43558.1533240334. The cubic root of 1897312721 is about 1237.9781308692.

The spelling of 1897312721 in words is "one billion, eight hundred ninety-seven million, three hundred twelve thousand, seven hundred twenty-one".