21731743 has 4 divisors (see below), whose sum is σ = 23707368. Its totient is φ = 19756120.

The previous prime is 21731737. The next prime is 21731767. The reversal of 21731743 is 34713712.

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-21731743 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 (21731243) 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, 987796 + ... + 987817.

It is an arithmetic number, because the mean of its divisors is an integer number (5926842).

Almost surely, 2^21731743 is an apocalyptic number.

21731743 is a deficient number, since it is larger than the sum of its proper divisors (1975625).

21731743 is a wasteful number, since it uses less digits than its factorization.

21731743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1975624.

The product of its digits is 3528, while the sum is 28.

The square root of 21731743 is about 4661.7317597648. The cubic root of 21731743 is about 279.0603835508.

It can be divided in two parts, 2173 and 1743, that added together give a triangular number (3916 = T₈₈).

The spelling of 21731743 in words is "twenty-one million, seven hundred thirty-one thousand, seven hundred forty-three".