20999993 has 4 divisors (see below), whose sum is σ = 24000000. Its totient is φ = 17999988.

The previous prime is 20999977. The next prime is 20999999. The reversal of 20999993 is 39999902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20999993 - 2⁴ = 20999977 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20999999) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1499993 + ... + 1500006.

It is an arithmetic number, because the mean of its divisors is an integer number (6000000).

Almost surely, 2^20999993 is an apocalyptic number.

It is an amenable number.

20999993 is a deficient number, since it is larger than the sum of its proper divisors (3000007).

20999993 is an equidigital number, since it uses as much as digits as its factorization.

20999993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3000006.

The product of its (nonzero) digits is 354294, while the sum is 50.

The square root of 20999993 is about 4582.5749311932. The cubic root of 20999993 is about 275.8923869834.

The spelling of 20999993 in words is "twenty million, nine hundred ninety-nine thousand, nine hundred ninety-three".