21245906 has 12 divisors (see below), whose sum is σ = 35029806. Its totient is φ = 9657120.

The previous prime is 21245867. The next prime is 21245911. The reversal of 21245906 is 60954212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21242881 + 3025 = 4609^2 + 55^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 43655 + ... + 44138.

Almost surely, 2^21245906 is an apocalyptic number.

21245906 is a deficient number, since it is larger than the sum of its proper divisors (13783900).

21245906 is a wasteful number, since it uses less digits than its factorization.

21245906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87817 (or 87806 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 21245906 is about 4609.3281506094. The cubic root of 21245906 is about 276.9651239612.

The spelling of 21245906 in words is "twenty-one million, two hundred forty-five thousand, nine hundred six".