21742 has 8 divisors (see below), whose sum is σ = 37296. Its totient is φ = 9312.

The previous prime is 21739. The next prime is 21751. The reversal of 21742 is 24712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 763 + ... + 790.

It is an arithmetic number, because the mean of its divisors is an integer number (4662).

2²¹⁷⁴² is an apocalyptic number.

21742 is a deficient number, since it is larger than the sum of its proper divisors (15554).

21742 is a wasteful number, since it uses less digits than its factorization.

21742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1562.

The product of its digits is 112, while the sum is 16.

The square root of 21742 is about 147.4516870029. The cubic root of 21742 is about 27.9104280508.

The spelling of 21742 in words is "twenty-one thousand, seven hundred forty-two", and thus it is an iban number.