21539347 has 4 divisors (see below), whose sum is σ = 21636160. Its totient is φ = 21442536.

The previous prime is 21539333. The next prime is 21539363. The reversal of 21539347 is 74393512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21539347 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21539387) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48072 + ... + 48517.

It is an arithmetic number, because the mean of its divisors is an integer number (5409040).

Almost surely, 2^21539347 is an apocalyptic number.

21539347 is a deficient number, since it is larger than the sum of its proper divisors (96813).

21539347 is an equidigital number, since it uses as much as digits as its factorization.

21539347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96812.

The product of its digits is 22680, while the sum is 34.

The square root of 21539347 is about 4641.0502044257. The cubic root of 21539347 is about 278.2344131567.

The spelling of 21539347 in words is "twenty-one million, five hundred thirty-nine thousand, three hundred forty-seven".