21916457 has 4 divisors (see below), whose sum is σ = 21952596. Its totient is φ = 21880320.

The previous prime is 21916439. The next prime is 21916459. The reversal of 21916457 is 75461912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8637721 + 13278736 = 2939^2 + 3644^2 .

It is a cyclic number.

It is not a de Polignac number, because 21916457 - 2⁶ = 21916393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21916459) 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 in 3 ways as a sum of consecutive naturals, for example, 17144 + ... + 18377.

It is an arithmetic number, because the mean of its divisors is an integer number (5488149).

Almost surely, 2^21916457 is an apocalyptic number.

It is an amenable number.

21916457 is a deficient number, since it is larger than the sum of its proper divisors (36139).

21916457 is an equidigital number, since it uses as much as digits as its factorization.

21916457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36138.

The product of its digits is 15120, while the sum is 35.

The square root of 21916457 is about 4681.5015753495. The cubic root of 21916457 is about 279.8488001696.

The spelling of 21916457 in words is "twenty-one million, nine hundred sixteen thousand, four hundred fifty-seven".