21675457 has 2 divisors, whose sum is σ = 21675458. Its totient is φ = 21675456.

The previous prime is 21675449. The next prime is 21675461. The reversal of 21675457 is 75457612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15992001 + 5683456 = 3999^2 + 2384^2 .

It is a cyclic number.

It is not a de Polignac number, because 21675457 - 2³ = 21675449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21675427) 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 as a sum of consecutive naturals, namely, 10837728 + 10837729.

It is an arithmetic number, because the mean of its divisors is an integer number (10837729).

Almost surely, 2^21675457 is an apocalyptic number.

It is an amenable number.

21675457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21675457 is an equidigital number, since it uses as much as digits as its factorization.

21675457 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 58800, while the sum is 37.

The square root of 21675457 is about 4655.6908187722. The cubic root of 21675457 is about 278.8192497551.

It can be divided in two parts, 216754 and 57, that added together give a triangular number (216811 = T₆₅₈).

The spelling of 21675457 in words is "twenty-one million, six hundred seventy-five thousand, four hundred fifty-seven".