21258139 has 8 divisors (see below), whose sum is σ = 24324608. Its totient is φ = 18199080.

The previous prime is 21258121. The next prime is 21258151. The reversal of 21258139 is 93185212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21258139 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21258139.

It is not an unprimeable number, because it can be changed into a prime (21258199) 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, 7384 + ... + 9850.

It is an arithmetic number, because the mean of its divisors is an integer number (3040576).

Almost surely, 2^21258139 is an apocalyptic number.

21258139 is a deficient number, since it is larger than the sum of its proper divisors (3066469).

21258139 is a wasteful number, since it uses less digits than its factorization.

21258139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3705.

The product of its digits is 4320, while the sum is 31.

The square root of 21258139 is about 4610.6549426302. The cubic root of 21258139 is about 277.0182708953.

The spelling of 21258139 in words is "twenty-one million, two hundred fifty-eight thousand, one hundred thirty-nine".