21370 has 8 divisors (see below), whose sum is σ = 38484. Its totient is φ = 8544.

The previous prime is 21347. The next prime is 21377. The reversal of 21370 is 7312.

It can be written as a sum of positive squares in 2 ways, for example, as 18769 + 2601 = 137^2 + 51^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 21370.

It is not an unprimeable number, because it can be changed into a prime (21377) 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, 1059 + ... + 1078.

2²¹³⁷⁰ is an apocalyptic number.

21370 is a deficient number, since it is larger than the sum of its proper divisors (17114).

21370 is a wasteful number, since it uses less digits than its factorization.

21370 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2144.

The product of its (nonzero) digits is 42, while the sum is 13.

The square root of 21370 is about 146.1848145328. The cubic root of 21370 is about 27.7503314085.

Adding to 21370 its product of nonzero digits (42), we get a palindrome (21412).

Adding to 21370 its reverse (7312), we get a palindrome (28682).

The spelling of 21370 in words is "twenty-one thousand, three hundred seventy", and thus it is an iban number.