21704 has 8 divisors (see below), whose sum is σ = 40710. Its totient is φ = 10848.

The previous prime is 21701. The next prime is 21713. The reversal of 21704 is 40712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 12100 + 9604 = 110^2 + 98^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (21701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1349 + ... + 1364.

2²¹⁷⁰⁴ is an apocalyptic number.

It is an amenable number.

21704 is a deficient number, since it is larger than the sum of its proper divisors (19006).

21704 is a wasteful number, since it uses less digits than its factorization.

21704 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2719 (or 2715 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 14.

The square root of 21704 is about 147.3227748856. The cubic root of 21704 is about 27.8941582387.

The spelling of 21704 in words is "twenty-one thousand, seven hundred four", and thus it is an iban number.