21254566 has 4 divisors (see below), whose sum is σ = 31881852. Its totient is φ = 10627282.

The previous prime is 21254491. The next prime is 21254567. The reversal of 21254566 is 66545212.

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

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21254567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5313640 + ... + 5313643.

It is an arithmetic number, because the mean of its divisors is an integer number (7970463).

Almost surely, 2^21254566 is an apocalyptic number.

21254566 is a deficient number, since it is larger than the sum of its proper divisors (10627286).

21254566 is a wasteful number, since it uses less digits than its factorization.

21254566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10627285.

The product of its digits is 14400, while the sum is 31.

The square root of 21254566 is about 4610.2674542807. The cubic root of 21254566 is about 277.0027499108.

Adding to 21254566 its reverse (66545212), we get a palindrome (87799778).

The spelling of 21254566 in words is "twenty-one million, two hundred fifty-four thousand, five hundred sixty-six".