21517139 has 8 divisors (see below), whose sum is σ = 25885440. Its totient is φ = 17472456.

The previous prime is 21517127. The next prime is 21517163. The reversal of 21517139 is 93171512.

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-21517139 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21517109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80759 + ... + 81024.

It is an arithmetic number, because the mean of its divisors is an integer number (3235680).

Almost surely, 2^21517139 is an apocalyptic number.

21517139 is a deficient number, since it is larger than the sum of its proper divisors (4368301).

21517139 is a wasteful number, since it uses less digits than its factorization.

21517139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161809.

The product of its digits is 1890, while the sum is 29.

The square root of 21517139 is about 4638.6570254762. The cubic root of 21517139 is about 278.1387563620.

The spelling of 21517139 in words is "twenty-one million, five hundred seventeen thousand, one hundred thirty-nine".