21680279 has 2 divisors, whose sum is σ = 21680280. Its totient is φ = 21680278.

The previous prime is 21680257. The next prime is 21680291. The reversal of 21680279 is 97208612.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21680279 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21680249) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840139 + 10840140.

It is an arithmetic number, because the mean of its divisors is an integer number (10840140).

Almost surely, 2^21680279 is an apocalyptic number.

21680279 is a deficient number, since it is larger than the sum of its proper divisors (1).

21680279 is an equidigital number, since it uses as much as digits as its factorization.

21680279 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21680279 is about 4656.2086508231. The cubic root of 21680279 is about 278.8399239326.

The spelling of 21680279 in words is "twenty-one million, six hundred eighty thousand, two hundred seventy-nine".