21671999 has 2 divisors, whose sum is σ = 21672000. Its totient is φ = 21671998.

The previous prime is 21671983. The next prime is 21672011. The reversal of 21671999 is 99917612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21671999 - 2⁴ = 21671983 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 (21671929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10835999 + 10836000.

It is an arithmetic number, because the mean of its divisors is an integer number (10836000).

Almost surely, 2^21671999 is an apocalyptic number.

21671999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21671999 is an equidigital number, since it uses as much as digits as its factorization.

21671999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 61236, while the sum is 44.

The square root of 21671999 is about 4655.3194305010. The cubic root of 21671999 is about 278.8044217980.

The spelling of 21671999 in words is "twenty-one million, six hundred seventy-one thousand, nine hundred ninety-nine".