21946399 has 4 divisors (see below), whose sum is σ = 22360536. Its totient is φ = 21532264.

The previous prime is 21946373. The next prime is 21946403. The reversal of 21946399 is 99364912.

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 21946399 - 2⁷ = 21946271 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21946369) 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, 206989 + ... + 207094.

It is an arithmetic number, because the mean of its divisors is an integer number (5590134).

Almost surely, 2^21946399 is an apocalyptic number.

21946399 is a deficient number, since it is larger than the sum of its proper divisors (414137).

21946399 is an equidigital number, since it uses as much as digits as its factorization.

21946399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 414136.

The product of its digits is 104976, while the sum is 43.

The square root of 21946399 is about 4684.6983894377. The cubic root of 21946399 is about 279.9761841989.

The spelling of 21946399 in words is "twenty-one million, nine hundred forty-six thousand, three hundred ninety-nine".