351997721 has 2 divisors, whose sum is σ = 351997722. Its totient is φ = 351997720.

The previous prime is 351997661. The next prime is 351997729. The reversal of 351997721 is 127799153.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 249987721 + 102010000 = 15811^2 + 10100^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-351997721 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (351997729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 175998860 + 175998861.

It is an arithmetic number, because the mean of its divisors is an integer number (175998861).

Almost surely, 2^351997721 is an apocalyptic number.

It is an amenable number.

351997721 is a deficient number, since it is larger than the sum of its proper divisors (1).

351997721 is an equidigital number, since it uses as much as digits as its factorization.

351997721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 119070, while the sum is 44.

The square root of 351997721 is about 18761.6023036413. The cubic root of 351997721 is about 706.0681432620.

The spelling of 351997721 in words is "three hundred fifty-one million, nine hundred ninety-seven thousand, seven hundred twenty-one".