21504139 has 4 divisors (see below), whose sum is σ = 21612400. Its totient is φ = 21395880.

The previous prime is 21504137. The next prime is 21504151. The reversal of 21504139 is 93140512.

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

It is a cyclic number.

It is not a de Polignac number, because 21504139 - 2¹ = 21504137 is a prime.

It is a super-3 number, since 3×21504139³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21504137) 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, 53832 + ... + 54229.

It is an arithmetic number, because the mean of its divisors is an integer number (5403100).

Almost surely, 2^21504139 is an apocalyptic number.

21504139 is a deficient number, since it is larger than the sum of its proper divisors (108261).

21504139 is a wasteful number, since it uses less digits than its factorization.

21504139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108260.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21504139 is about 4637.2555461178. The cubic root of 21504139 is about 278.0827307559.

The spelling of 21504139 in words is "twenty-one million, five hundred four thousand, one hundred thirty-nine".