21821139 has 12 divisors (see below), whose sum is σ = 33178600. Its totient is φ = 13781664.

The previous prime is 21821123. The next prime is 21821141. The reversal of 21821139 is 93112812.

It is not a de Polignac number, because 21821139 - 2⁴ = 21821123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21821119) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 63634 + ... + 63975.

Almost surely, 2^21821139 is an apocalyptic number.

21821139 is a deficient number, since it is larger than the sum of its proper divisors (11357461).

21821139 is a wasteful number, since it uses less digits than its factorization.

21821139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127634 (or 127631 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 21821139 is about 4671.3102016458. The cubic root of 21821139 is about 279.4425089473.

It can be divided in two parts, 2182 and 1139, that added together give a triangular number (3321 = T₈₁).

The spelling of 21821139 in words is "twenty-one million, eight hundred twenty-one thousand, one hundred thirty-nine".