21255706 has 4 divisors (see below), whose sum is σ = 31883562. Its totient is φ = 10627852.

The previous prime is 21255679. The next prime is 21255721. The reversal of 21255706 is 60755212.

21255706 is nontrivially palindromic in base 15.

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

It can be written as a sum of positive squares in only one way, i.e., 14707225 + 6548481 = 3835^2 + 2559^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5313925 + ... + 5313928.

Almost surely, 2^21255706 is an apocalyptic number.

21255706 is a deficient number, since it is larger than the sum of its proper divisors (10627856).

21255706 is a wasteful number, since it uses less digits than its factorization.

21255706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10627855.

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 21255706 is about 4610.3910897016. The cubic root of 21255706 is about 277.0077022191.

The spelling of 21255706 in words is "twenty-one million, two hundred fifty-five thousand, seven hundred six".