21770 has 16 divisors (see below), whose sum is σ = 44928. Its totient is φ = 7440.

The previous prime is 21767. The next prime is 21773. The reversal of 21770 is 7712.

It is a happy number.

21770 is nontrivially palindromic in base 6.

It is an interprime number because it is at equal distance from previous prime (21767) and next prime (21773).

It is a Curzon number.

It is a zygodrome in base 4.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21770.

It is not an unprimeable number, because it can be changed into a prime (21773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86 + ... + 225.

It is an arithmetic number, because the mean of its divisors is an integer number (2808).

2²¹⁷⁷⁰ is an apocalyptic number.

21770 is an abundant number, since it is smaller than the sum of its proper divisors (23158).

It is a weird number, because it is abundant, but not a pseudoperfect number.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22464).

21770 is a wasteful number, since it uses less digits than its factorization.

21770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325.

The product of its (nonzero) digits is 98, while the sum is 17.

The square root of 21770 is about 147.5466028074. The cubic root of 21770 is about 27.9224042067.

The spelling of 21770 in words is "twenty-one thousand, seven hundred seventy", and thus it is an iban number.