21743989 has 4 divisors (see below), whose sum is σ = 22445440. Its totient is φ = 21042540.

The previous prime is 21743983. The next prime is 21744001. The reversal of 21743989 is 98934712.

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 21743989 - 2⁷ = 21743861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21743983) 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, 350679 + ... + 350740.

It is an arithmetic number, because the mean of its divisors is an integer number (5611360).

Almost surely, 2^21743989 is an apocalyptic number.

It is an amenable number.

21743989 is a deficient number, since it is larger than the sum of its proper divisors (701451).

21743989 is an equidigital number, since it uses as much as digits as its factorization.

21743989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 701450.

The product of its digits is 108864, while the sum is 43.

The square root of 21743989 is about 4663.0450351675. The cubic root of 21743989 is about 279.1127912470.

The spelling of 21743989 in words is "twenty-one million, seven hundred forty-three thousand, nine hundred eighty-nine".