21378256 has 10 divisors (see below), whose sum is σ = 41420402. Its totient is φ = 10689120.

The previous prime is 21378233. The next prime is 21378271. The reversal of 21378256 is 65287312.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21344400 + 33856 = 4620^2 + 184^2 .

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, 668055 + ... + 668086.

Almost surely, 2^21378256 is an apocalyptic number.

It is an amenable number.

21378256 is a deficient number, since it is larger than the sum of its proper divisors (20042146).

21378256 is a wasteful number, since it uses less digits than its factorization.

21378256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1336149 (or 1336143 counting only the distinct ones).

The product of its digits is 20160, while the sum is 34.

The square root of 21378256 is about 4623.6626174495. The cubic root of 21378256 is about 277.5390459896.

The spelling of 21378256 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred fifty-six".