21105457 has 2 divisors, whose sum is σ = 21105458. Its totient is φ = 21105456.

The previous prime is 21105443. The next prime is 21105473. The reversal of 21105457 is 75450112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19722481 + 1382976 = 4441^2 + 1176^2 .

It is a cyclic number.

It is not a de Polignac number, because 21105457 - 2²³ = 12716849 is a prime.

It is not a weakly prime, because it can be changed into another prime (21105407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552728 + 10552729.

It is an arithmetic number, because the mean of its divisors is an integer number (10552729).

Almost surely, 2^21105457 is an apocalyptic number.

It is an amenable number.

21105457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105457 is an equidigital number, since it uses as much as digits as its factorization.

21105457 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21105457 is about 4594.0675876613. The cubic root of 21105457 is about 276.3534687451.

Adding to 21105457 its reverse (75450112), we get a palindrome (96555569).

The spelling of 21105457 in words is "twenty-one million, one hundred five thousand, four hundred fifty-seven".