21202101997 has 2 divisors, whose sum is σ = 21202101998. Its totient is φ = 21202101996.

The previous prime is 21202101959. The next prime is 21202102001. The reversal of 21202101997 is 79910120212.

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., 16376576841 + 4825525156 = 127971^2 + 69466^2 .

It is a cyclic number.

It is not a de Polignac number, because 21202101997 - 2²³ = 21193713389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21202501997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601050998 + 10601050999.

It is an arithmetic number, because the mean of its divisors is an integer number (10601050999).

Almost surely, 2^21202101997 is an apocalyptic number.

It is an amenable number.

21202101997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21202101997 is an equidigital number, since it uses as much as digits as its factorization.

21202101997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 34.

The spelling of 21202101997 in words is "twenty-one billion, two hundred two million, one hundred one thousand, nine hundred ninety-seven".