21680273 has 4 divisors (see below), whose sum is σ = 22821360. Its totient is φ = 20539188.

The previous prime is 21680257. The next prime is 21680279. The reversal of 21680273 is 37208612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21680273 - 2⁴ = 21680257 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21680279) 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, 570515 + ... + 570552.

It is an arithmetic number, because the mean of its divisors is an integer number (5705340).

Almost surely, 2^21680273 is an apocalyptic number.

It is an amenable number.

21680273 is a deficient number, since it is larger than the sum of its proper divisors (1141087).

21680273 is a wasteful number, since it uses less digits than its factorization.

21680273 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1141086.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21680273 is about 4656.2080065220. The cubic root of 21680273 is about 278.8398982097.

Adding to 21680273 its reverse (37208612), we get a palindrome (58888885).

The spelling of 21680273 in words is "twenty-one million, six hundred eighty thousand, two hundred seventy-three".