21743581 has 4 divisors (see below), whose sum is σ = 22888000. Its totient is φ = 20599164.

The previous prime is 21743551. The next prime is 21743587. The reversal of 21743581 is 18534712.

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 21743581 - 2⁷ = 21743453 is a prime.

It is a super-2 number, since 2×21743581² = 945566629407122, 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 (21743587) 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, 572181 + ... + 572218.

It is an arithmetic number, because the mean of its divisors is an integer number (5722000).

Almost surely, 2^21743581 is an apocalyptic number.

It is an amenable number.

21743581 is a deficient number, since it is larger than the sum of its proper divisors (1144419).

21743581 is a wasteful number, since it uses less digits than its factorization.

21743581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1144418.

The product of its digits is 6720, while the sum is 31.

The square root of 21743581 is about 4663.0012867251. The cubic root of 21743581 is about 279.1110454966. Note that the first 3 decimals are identical.

The spelling of 21743581 in words is "twenty-one million, seven hundred forty-three thousand, five hundred eighty-one".