21278656 has 28 divisors (see below), whose sum is σ = 48257968. Its totient is φ = 9119232.

The previous prime is 21278641. The next prime is 21278659. The reversal of 21278656 is 65687212.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21278659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23301 + ... + 24196.

Almost surely, 2^21278656 is an apocalyptic number.

It is an amenable number.

21278656 is an abundant number, since it is smaller than the sum of its proper divisors (26979312).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21278656 is an equidigital number, since it uses as much as digits as its factorization.

21278656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47516 (or 47506 counting only the distinct ones).

The product of its digits is 40320, while the sum is 37.

The square root of 21278656 is about 4612.8793610932. The cubic root of 21278656 is about 277.1073623623.

The spelling of 21278656 in words is "twenty-one million, two hundred seventy-eight thousand, six hundred fifty-six".