21315689 has 2 divisors, whose sum is σ = 21315690. Its totient is φ = 21315688.

The previous prime is 21315661. The next prime is 21315709. The reversal of 21315689 is 98651312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14899600 + 6416089 = 3860^2 + 2533^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21315689 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21315649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10657844 + 10657845.

It is an arithmetic number, because the mean of its divisors is an integer number (10657845).

Almost surely, 2^21315689 is an apocalyptic number.

It is an amenable number.

21315689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21315689 is an equidigital number, since it uses as much as digits as its factorization.

21315689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 35.

The square root of 21315689 is about 4616.8917033000. The cubic root of 21315689 is about 277.2680267916.

The spelling of 21315689 in words is "twenty-one million, three hundred fifteen thousand, six hundred eighty-nine".