21999893 has 4 divisors (see below), whose sum is σ = 22758540. Its totient is φ = 21241248.

The previous prime is 21999889. The next prime is 21999907. The reversal of 21999893 is 39899912.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16056049 + 5943844 = 4007^2 + 2438^2 .

It is a cyclic number.

It is not a de Polignac number, because 21999893 - 2² = 21999889 is a prime.

It is a super-2 number, since 2×21999893² = 967990584022898, 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 (21999193) 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, 379280 + ... + 379337.

It is an arithmetic number, because the mean of its divisors is an integer number (5689635).

Almost surely, 2^21999893 is an apocalyptic number.

It is an amenable number.

21999893 is a deficient number, since it is larger than the sum of its proper divisors (758647).

21999893 is an equidigital number, since it uses as much as digits as its factorization.

21999893 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 758646.

The product of its digits is 314928, while the sum is 50.

The square root of 21999893 is about 4690.4043535712. The cubic root of 21999893 is about 280.2034787948.

The spelling of 21999893 in words is "twenty-one million, nine hundred ninety-nine thousand, eight hundred ninety-three".