21939321 has 16 divisors (see below), whose sum is σ = 30051648. Its totient is φ = 14232000.

The previous prime is 21939277. The next prime is 21939361. The reversal of 21939321 is 12393912.

It is a happy number.

It is not a de Polignac number, because 21939321 - 2¹⁴ = 21922937 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21939361) 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, 17890 + ... + 19076.

It is an arithmetic number, because the mean of its divisors is an integer number (1878228).

Almost surely, 2^21939321 is an apocalyptic number.

It is an amenable number.

21939321 is a deficient number, since it is larger than the sum of its proper divisors (8112327).

21939321 is a wasteful number, since it uses less digits than its factorization.

21939321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1352.

The product of its digits is 2916, while the sum is 30.

The square root of 21939321 is about 4683.9428903436. The cubic root of 21939321 is about 279.9460823052.

The spelling of 21939321 in words is "twenty-one million, nine hundred thirty-nine thousand, three hundred twenty-one".