21256306 has 4 divisors (see below), whose sum is σ = 31884462. Its totient is φ = 10628152.

The previous prime is 21256303. The next prime is 21256309. The reversal of 21256306 is 60365212.

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

It is an interprime number because it is at equal distance from previous prime (21256303) and next prime (21256309).

It can be written as a sum of positive squares in only one way, i.e., 13388281 + 7868025 = 3659^2 + 2805^2 .

It is not an unprimeable number, because it can be changed into a prime (21256303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5314075 + ... + 5314078.

Almost surely, 2^21256306 is an apocalyptic number.

21256306 is a deficient number, since it is larger than the sum of its proper divisors (10628156).

21256306 is a wasteful number, since it uses less digits than its factorization.

21256306 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10628155.

The product of its (nonzero) digits is 2160, while the sum is 25.

The square root of 21256306 is about 4610.4561596441. The cubic root of 21256306 is about 277.0103086260.

The spelling of 21256306 in words is "twenty-one million, two hundred fifty-six thousand, three hundred six".