21307245 has 8 divisors (see below), whose sum is σ = 34091616. Its totient is φ = 11363856.

The previous prime is 21307243. The next prime is 21307271. The reversal of 21307245 is 54270312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21307245 - 2¹ = 21307243 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21307243) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 710227 + ... + 710256.

It is an arithmetic number, because the mean of its divisors is an integer number (4261452).

Almost surely, 2^21307245 is an apocalyptic number.

It is an amenable number.

21307245 is a deficient number, since it is larger than the sum of its proper divisors (12784371).

21307245 is a wasteful number, since it uses less digits than its factorization.

21307245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1420491.

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21307245 is about 4615.9771446575. The cubic root of 21307245 is about 277.2314096244.

Adding to 21307245 its reverse (54270312), we get a palindrome (75577557).

The spelling of 21307245 in words is "twenty-one million, three hundred seven thousand, two hundred forty-five".