21240945 has 72 divisors (see below), whose sum is σ = 41827968. Its totient is φ = 9958080.

The previous prime is 21240913. The next prime is 21240971. The reversal of 21240945 is 54904212.

21240945 is a `hidden beast` number, since 212 + 409 + 45 = 666.

It is not a de Polignac number, because 21240945 - 2⁵ = 21240913 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 255874 + ... + 255956.

It is an arithmetic number, because the mean of its divisors is an integer number (580944).

Almost surely, 2^21240945 is an apocalyptic number.

It is an amenable number.

21240945 is a deficient number, since it is larger than the sum of its proper divisors (20587023).

21240945 is a wasteful number, since it uses less digits than its factorization.

21240945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163 (or 149 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21240945 is about 4608.7899713482. The cubic root of 21240945 is about 276.9435648125.

The spelling of 21240945 in words is "twenty-one million, two hundred forty thousand, nine hundred forty-five".