21815116997 has 2 divisors, whose sum is σ = 21815116998. Its totient is φ = 21815116996.

The previous prime is 21815116951. The next prime is 21815117011. The reversal of 21815116997 is 79961151812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16107163396 + 5707953601 = 126914^2 + 75551^2 .

It is a cyclic number.

It is not a de Polignac number, because 21815116997 - 2²⁰ = 21814068421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21815116597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10907558498 + 10907558499.

It is an arithmetic number, because the mean of its divisors is an integer number (10907558499).

Almost surely, 2^21815116997 is an apocalyptic number.

It is an amenable number.

21815116997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21815116997 is an equidigital number, since it uses as much as digits as its factorization.

21815116997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 272160, while the sum is 50.

The spelling of 21815116997 in words is "twenty-one billion, eight hundred fifteen million, one hundred sixteen thousand, nine hundred ninety-seven".