21109457 has 2 divisors, whose sum is σ = 21109458. Its totient is φ = 21109456.

The previous prime is 21109447. The next prime is 21109463. The reversal of 21109457 is 75490112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14432401 + 6677056 = 3799^2 + 2584^2 .

It is a cyclic number.

It is not a de Polignac number, because 21109457 - 2⁴ = 21109441 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21109447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554728 + 10554729.

It is an arithmetic number, because the mean of its divisors is an integer number (10554729).

Almost surely, 2^21109457 is an apocalyptic number.

It is an amenable number.

21109457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21109457 is an equidigital number, since it uses as much as digits as its factorization.

21109457 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 21109457 is about 4594.5029110884. The cubic root of 21109457 is about 276.3709262215.

Adding to 21109457 its reverse (75490112), we get a palindrome (96599569).

The spelling of 21109457 in words is "twenty-one million, one hundred nine thousand, four hundred fifty-seven".