21137917 has 2 divisors, whose sum is σ = 21137918. Its totient is φ = 21137916.

The previous prime is 21137911. The next prime is 21137923. The reversal of 21137917 is 71973112.

It is a balanced prime because it is at equal distance from previous prime (21137911) and next prime (21137923).

It can be written as a sum of positive squares in only one way, i.e., 15912121 + 5225796 = 3989^2 + 2286^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21137917 is a prime.

It is a super-3 number, since 3×21137917³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21137911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10568958 + 10568959.

It is an arithmetic number, because the mean of its divisors is an integer number (10568959).

Almost surely, 2^21137917 is an apocalyptic number.

It is an amenable number.

21137917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21137917 is an equidigital number, since it uses as much as digits as its factorization.

21137917 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2646, while the sum is 31.

The square root of 21137917 is about 4597.5990473289. The cubic root of 21137917 is about 276.4950725447.

The spelling of 21137917 in words is "twenty-one million, one hundred thirty-seven thousand, nine hundred seventeen".