21254657 has 4 divisors (see below), whose sum is σ = 21603156. Its totient is φ = 20906160.

The previous prime is 21254647. The next prime is 21254677. The reversal of 21254657 is 75645212.

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 9991921 + 11262736 = 3161^2 + 3356^2 .

It is a cyclic number.

It is not a de Polignac number, because 21254657 - 2¹⁸ = 20992513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21254617) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 174158 + ... + 174279.

It is an arithmetic number, because the mean of its divisors is an integer number (5400789).

Almost surely, 2^21254657 is an apocalyptic number.

It is an amenable number.

21254657 is a deficient number, since it is larger than the sum of its proper divisors (348499).

21254657 is an equidigital number, since it uses as much as digits as its factorization.

21254657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 348498.

The product of its digits is 16800, while the sum is 32.

The square root of 21254657 is about 4610.2773235457. The cubic root of 21254657 is about 277.0031452331.

Adding to 21254657 its reverse (75645212), we get a palindrome (96899869).

The spelling of 21254657 in words is "twenty-one million, two hundred fifty-four thousand, six hundred fifty-seven".