21243899 has 4 divisors (see below), whose sum is σ = 21362760. Its totient is φ = 21125040.

The previous prime is 21243857. The next prime is 21243907. The reversal of 21243899 is 99834212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21243899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21240899) 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, 59162 + ... + 59519.

It is an arithmetic number, because the mean of its divisors is an integer number (5340690).

Almost surely, 2^21243899 is an apocalyptic number.

21243899 is a deficient number, since it is larger than the sum of its proper divisors (118861).

21243899 is a wasteful number, since it uses less digits than its factorization.

21243899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118860.

The product of its digits is 31104, while the sum is 38.

The square root of 21243899 is about 4609.1104347802. The cubic root of 21243899 is about 276.9564024926.

The spelling of 21243899 in words is "twenty-one million, two hundred forty-three thousand, eight hundred ninety-nine".