21909999 has 8 divisors (see below), whose sum is σ = 29427120. Its totient is φ = 14499776.

The previous prime is 21909989. The next prime is 21910013. The reversal of 21909999 is 99990912.

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 21909999 - 2⁸ = 21909743 is a prime.

21909999 is a modest number, since divided by 9999 gives 2190 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909989) 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, 26244 + ... + 27065.

It is an arithmetic number, because the mean of its divisors is an integer number (3678390).

Almost surely, 2^21909999 is an apocalyptic number.

21909999 is a deficient number, since it is larger than the sum of its proper divisors (7517121).

21909999 is a wasteful number, since it uses less digits than its factorization.

21909999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53449.

The product of its (nonzero) digits is 118098, while the sum is 48.

The square root of 21909999 is about 4680.8117885683. The cubic root of 21909999 is about 279.8213103083.

The spelling of 21909999 in words is "twenty-one million, nine hundred nine thousand, nine hundred ninety-nine".