971999921 has 2 divisors, whose sum is σ = 971999922. Its totient is φ = 971999920.

The previous prime is 971999911. The next prime is 972000017. The reversal of 971999921 is 129999179.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 692742400 + 279257521 = 26320^2 + 16711^2 .

It is an emirp because it is prime and its reverse (129999179) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-971999921 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (971999911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 485999960 + 485999961.

It is an arithmetic number, because the mean of its divisors is an integer number (485999961).

Almost surely, 2^971999921 is an apocalyptic number.

It is an amenable number.

971999921 is a deficient number, since it is larger than the sum of its proper divisors (1).

971999921 is an equidigital number, since it uses as much as digits as its factorization.

971999921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 826686, while the sum is 56.

The square root of 971999921 is about 31176.9132692767. The cubic root of 971999921 is about 990.5781478317.

The spelling of 971999921 in words is "nine hundred seventy-one million, nine hundred ninety-nine thousand, nine hundred twenty-one".