21042656 has 12 divisors (see below), whose sum is σ = 41427792. Its totient is φ = 10521312.

The previous prime is 21042649. The next prime is 21042689. The reversal of 21042656 is 65624012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328760 + ... + 328823.

It is an arithmetic number, because the mean of its divisors is an integer number (3452316).

Almost surely, 2^21042656 is an apocalyptic number.

It is an amenable number.

21042656 is a deficient number, since it is larger than the sum of its proper divisors (20385136).

21042656 is an equidigital number, since it uses as much as digits as its factorization.

21042656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 657593 (or 657585 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21042656 is about 4587.2274850938. The cubic root of 21042656 is about 276.0790923645.

Adding to 21042656 its reverse (65624012), we get a palindrome (86666668).

The spelling of 21042656 in words is "twenty-one million, forty-two thousand, six hundred fifty-six".