21247245 has 32 divisors (see below), whose sum is σ = 38999040. Its totient is φ = 10964160.

The previous prime is 21247231. The next prime is 21247249. The reversal of 21247245 is 54274212.

It is not a de Polignac number, because 21247245 - 2⁶ = 21247181 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21247249) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1647 + ... + 6723.

It is an arithmetic number, because the mean of its divisors is an integer number (1218720).

Almost surely, 2^21247245 is an apocalyptic number.

It is an amenable number.

21247245 is a deficient number, since it is larger than the sum of its proper divisors (17751795).

21247245 is a wasteful number, since it uses less digits than its factorization.

21247245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5122 (or 5116 counting only the distinct ones).

The product of its digits is 4480, while the sum is 27.

The square root of 21247245 is about 4609.4733972548. The cubic root of 21247245 is about 276.9709423137.

The spelling of 21247245 in words is "twenty-one million, two hundred forty-seven thousand, two hundred forty-five".