21185739 has 16 divisors (see below), whose sum is σ = 31552000. Its totient is φ = 14049288.

The previous prime is 21185729. The next prime is 21185771. The reversal of 21185739 is 93758112.

It is a de Polignac number, because none of the positive numbers 2^k-21185739 is a prime.

It is a super-2 number, since 2×21185739² = 897671073952242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21185729) 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 15 ways as a sum of consecutive naturals, for example, 3402 + ... + 7344.

It is an arithmetic number, because the mean of its divisors is an integer number (1972000).

Almost surely, 2^21185739 is an apocalyptic number.

21185739 is a deficient number, since it is larger than the sum of its proper divisors (10366261).

21185739 is a wasteful number, since it uses less digits than its factorization.

21185739 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4151 (or 4145 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21185739 is about 4602.7968671233. The cubic root of 21185739 is about 276.7034278018.

The spelling of 21185739 in words is "twenty-one million, one hundred eighty-five thousand, seven hundred thirty-nine".