21994391 has 8 divisors (see below), whose sum is σ = 22758960. Its totient is φ = 21238848.

The previous prime is 21994369. The next prime is 21994393. The reversal of 21994391 is 19349912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21994391 - 2¹⁴ = 21978007 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 (21994393) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2900 + ... + 7238.

It is an arithmetic number, because the mean of its divisors is an integer number (2844870).

Almost surely, 2^21994391 is an apocalyptic number.

21994391 is a deficient number, since it is larger than the sum of its proper divisors (764569).

21994391 is a wasteful number, since it uses less digits than its factorization.

21994391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4513.

The product of its digits is 17496, while the sum is 38.

The square root of 21994391 is about 4689.8178002989. The cubic root of 21994391 is about 280.1801179527.

The spelling of 21994391 in words is "twenty-one million, nine hundred ninety-four thousand, three hundred ninety-one".