21511139 has 4 divisors (see below), whose sum is σ = 23165856. Its totient is φ = 19856424.

The previous prime is 21511109. The next prime is 21511151. The reversal of 21511139 is 93111512.

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 21511139 - 2⁸ = 21510883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21511109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 827339 + ... + 827364.

It is an arithmetic number, because the mean of its divisors is an integer number (5791464).

Almost surely, 2^21511139 is an apocalyptic number.

21511139 is a deficient number, since it is larger than the sum of its proper divisors (1654717).

21511139 is a wasteful number, since it uses less digits than its factorization.

21511139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1654716.

The product of its digits is 270, while the sum is 23.

The square root of 21511139 is about 4638.0102414721. The cubic root of 21511139 is about 278.1129011949.

The spelling of 21511139 in words is "twenty-one million, five hundred eleven thousand, one hundred thirty-nine".