21915457 has 2 divisors, whose sum is σ = 21915458. Its totient is φ = 21915456.

The previous prime is 21915451. The next prime is 21915463. The reversal of 21915457 is 75451912.

It is a balanced prime because it is at equal distance from previous prime (21915451) and next prime (21915463).

It can be written as a sum of positive squares in only one way, i.e., 11669056 + 10246401 = 3416^2 + 3201^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21915457 is a prime.

It is not a weakly prime, because it can be changed into another prime (21915451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10957728 + 10957729.

It is an arithmetic number, because the mean of its divisors is an integer number (10957729).

Almost surely, 2^21915457 is an apocalyptic number.

It is an amenable number.

21915457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21915457 is an equidigital number, since it uses as much as digits as its factorization.

21915457 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12600, while the sum is 34.

The square root of 21915457 is about 4681.3947707921. The cubic root of 21915457 is about 279.8445438086.

The spelling of 21915457 in words is "twenty-one million, nine hundred fifteen thousand, four hundred fifty-seven".