21990439 has 16 divisors (see below), whose sum is σ = 23927040. Its totient is φ = 20160000.

The previous prime is 21990433. The next prime is 21990443. The reversal of 21990439 is 93409912.

It is a cyclic number.

It is not a de Polignac number, because 21990439 - 2¹⁵ = 21957671 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21990398 and 21990407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21990433) 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 15 ways as a sum of consecutive naturals, for example, 54639 + ... + 55039.

It is an arithmetic number, because the mean of its divisors is an integer number (1495440).

Almost surely, 2^21990439 is an apocalyptic number.

21990439 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21990439 is a deficient number, since it is larger than the sum of its proper divisors (1936601).

21990439 is a wasteful number, since it uses less digits than its factorization.

21990439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 522.

The product of its (nonzero) digits is 17496, while the sum is 37.

The square root of 21990439 is about 4689.3964430404. The cubic root of 21990439 is about 280.1633358232.

The spelling of 21990439 in words is "twenty-one million, nine hundred ninety thousand, four hundred thirty-nine".