21255506 has 4 divisors (see below), whose sum is σ = 31883262. Its totient is φ = 10627752.

The previous prime is 21255497. The next prime is 21255529. The reversal of 21255506 is 60555212.

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., 20025625 + 1229881 = 4475^2 + 1109^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5313875 + ... + 5313878.

Almost surely, 2^21255506 is an apocalyptic number.

21255506 is a deficient number, since it is larger than the sum of its proper divisors (10627756).

21255506 is a wasteful number, since it uses less digits than its factorization.

21255506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10627755.

The product of its (nonzero) digits is 3000, while the sum is 26.

The square root of 21255506 is about 4610.3693995167. The cubic root of 21255506 is about 277.0068334059.

The spelling of 21255506 in words is "twenty-one million, two hundred fifty-five thousand, five hundred six".