21145239 has 16 divisors (see below), whose sum is σ = 31440640. Its totient is φ = 14045400.

The previous prime is 21145213. The next prime is 21145249. The reversal of 21145239 is 93254112.

It is not a de Polignac number, because 21145239 - 2⁹ = 21144727 is a prime.

It is a super-2 number, since 2×21145239² = 894242264734242, which contains 22 as substring.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21145249) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7014 + ... + 9564.

It is an arithmetic number, because the mean of its divisors is an integer number (1965040).

Almost surely, 2^21145239 is an apocalyptic number.

21145239 is a deficient number, since it is larger than the sum of its proper divisors (10295401).

21145239 is a wasteful number, since it uses less digits than its factorization.

21145239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2867 (or 2861 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 21145239 is about 4598.3952635675. The cubic root of 21145239 is about 276.5269940629.

The spelling of 21145239 in words is "twenty-one million, one hundred forty-five thousand, two hundred thirty-nine".