21681683 has 2 divisors, whose sum is σ = 21681684. Its totient is φ = 21681682.

The previous prime is 21681659. The next prime is 21681689. The reversal of 21681683 is 38618612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21681683 - 2⁶ = 21681619 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21681689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840841 + 10840842.

It is an arithmetic number, because the mean of its divisors is an integer number (10840842).

Almost surely, 2^21681683 is an apocalyptic number.

21681683 is a deficient number, since it is larger than the sum of its proper divisors (1).

21681683 is an equidigital number, since it uses as much as digits as its factorization.

21681683 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 35.

The square root of 21681683 is about 4656.3594148218. The cubic root of 21681683 is about 278.8459429635.

The spelling of 21681683 in words is "twenty-one million, six hundred eighty-one thousand, six hundred eighty-three".