21135997 has 2 divisors, whose sum is σ = 21135998. Its totient is φ = 21135996.

The previous prime is 21135971. The next prime is 21136007. The reversal of 21135997 is 79953112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15476356 + 5659641 = 3934^2 + 2379^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21135997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21135797) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567998 + 10567999.

It is an arithmetic number, because the mean of its divisors is an integer number (10567999).

Almost surely, 2^21135997 is an apocalyptic number.

It is an amenable number.

21135997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135997 is an equidigital number, since it uses as much as digits as its factorization.

21135997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17010, while the sum is 37.

The square root of 21135997 is about 4597.3902379502. The cubic root of 21135997 is about 276.4867007546.

The spelling of 21135997 in words is "twenty-one million, one hundred thirty-five thousand, nine hundred ninety-seven".