21915697 has 2 divisors, whose sum is σ = 21915698. Its totient is φ = 21915696.

The previous prime is 21915679. The next prime is 21915701. The reversal of 21915697 is 79651912.

Together with previous prime (21915679) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21169201 + 746496 = 4601^2 + 864^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21915697 is a prime.

It is not a weakly prime, because it can be changed into another prime (21915617) 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, 10957848 + 10957849.

It is an arithmetic number, because the mean of its divisors is an integer number (10957849).

Almost surely, 2^21915697 is an apocalyptic number.

It is an amenable number.

21915697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21915697 is an equidigital number, since it uses as much as digits as its factorization.

21915697 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34020, while the sum is 40.

The square root of 21915697 is about 4681.4204041081. The cubic root of 21915697 is about 279.8455653471.

The spelling of 21915697 in words is "twenty-one million, nine hundred fifteen thousand, six hundred ninety-seven".