21662 has 4 divisors (see below), whose sum is σ = 32496. Its totient is φ = 10830.

The previous prime is 21661. The next prime is 21673. The reversal of 21662 is 26612.

It is a semiprime because it is the product of two primes.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 21662.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5414 + ... + 5417.

It is an arithmetic number, because the mean of its divisors is an integer number (8124).

2²¹⁶⁶² is an apocalyptic number.

21662 is a deficient number, since it is larger than the sum of its proper divisors (10834).

21662 is a wasteful number, since it uses less digits than its factorization.

21662 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10833.

The product of its digits is 144, while the sum is 17.

The square root of 21662 is about 147.1801617067. The cubic root of 21662 is about 27.8761537056.

Subtracting 21662 from its reverse (26612), we obtain a triangular number (4950 = T₉₉).

The spelling of 21662 in words is "twenty-one thousand, six hundred sixty-two".