21693999 has 4 divisors (see below), whose sum is σ = 28925336. Its totient is φ = 14462664.

The previous prime is 21693977. The next prime is 21694007. The reversal of 21693999 is 99939612.

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

It is not a de Polignac number, because 21693999 - 2⁵ = 21693967 is a prime.

It is a super-2 number, since 2×21693999² = 941259185224002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21693949) 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, 3615664 + ... + 3615669.

It is an arithmetic number, because the mean of its divisors is an integer number (7231334).

Almost surely, 2^21693999 is an apocalyptic number.

21693999 is a deficient number, since it is larger than the sum of its proper divisors (7231337).

21693999 is an equidigital number, since it uses as much as digits as its factorization.

21693999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7231336.

The product of its digits is 236196, while the sum is 48.

The square root of 21693999 is about 4657.6817194823. The cubic root of 21693999 is about 278.8987312483.

The spelling of 21693999 in words is "twenty-one million, six hundred ninety-three thousand, nine hundred ninety-nine".