971511721 has 2 divisors, whose sum is σ = 971511722. Its totient is φ = 971511720.

The previous prime is 971511707. The next prime is 971511787. The reversal of 971511721 is 127115179.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 944886121 + 26625600 = 30739^2 + 5160^2 .

It is a cyclic number.

It is not a de Polignac number, because 971511721 - 2⁵ = 971511689 is a prime.

It is not a weakly prime, because it can be changed into another prime (971511791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 485755860 + 485755861.

It is an arithmetic number, because the mean of its divisors is an integer number (485755861).

Almost surely, 2^971511721 is an apocalyptic number.

It is an amenable number.

971511721 is a deficient number, since it is larger than the sum of its proper divisors (1).

971511721 is an equidigital number, since it uses as much as digits as its factorization.

971511721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4410, while the sum is 34.

The square root of 971511721 is about 31169.0827744417. The cubic root of 971511721 is about 990.4122763370.

The spelling of 971511721 in words is "nine hundred seventy-one million, five hundred eleven thousand, seven hundred twenty-one".