21799999 has 4 divisors (see below), whose sum is σ = 23476936. Its totient is φ = 20123064.

The previous prime is 21799979. The next prime is 21800003. The reversal of 21799999 is 99999712.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21799999 - 2⁷ = 21799871 is a prime.

It is a Duffinian number.

21799999 is a modest number, since divided by 9999 gives 2179 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21799979) 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, 838449 + ... + 838474.

It is an arithmetic number, because the mean of its divisors is an integer number (5869234).

Almost surely, 2^21799999 is an apocalyptic number.

21799999 is a deficient number, since it is larger than the sum of its proper divisors (1676937).

21799999 is a wasteful number, since it uses less digits than its factorization.

21799999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1676936.

The product of its digits is 826686, while the sum is 55.

The square root of 21799999 is about 4669.0469048833. The cubic root of 21799999 is about 279.3522398533.

The spelling of 21799999 in words is "twenty-one million, seven hundred ninety-nine thousand, nine hundred ninety-nine".