21308247 has 6 divisors (see below), whose sum is σ = 30778592. Its totient is φ = 14205492.

The previous prime is 21308219. The next prime is 21308299. The reversal of 21308247 is 74280312.

It is not a de Polignac number, because 21308247 - 2⁸ = 21307991 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21308247.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308207) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1183783 + ... + 1183800.

Almost surely, 2^21308247 is an apocalyptic number.

21308247 is a deficient number, since it is larger than the sum of its proper divisors (9470345).

21308247 is a wasteful number, since it uses less digits than its factorization.

21308247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2367589 (or 2367586 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21308247 is about 4616.0856794475. The cubic root of 21308247 is about 277.2357552749.

Adding to 21308247 its reverse (74280312), we get a palindrome (95588559).

The spelling of 21308247 in words is "twenty-one million, three hundred eight thousand, two hundred forty-seven".