21611999 has 2 divisors, whose sum is σ = 21612000. Its totient is φ = 21611998.

The previous prime is 21611977. The next prime is 21612011. The reversal of 21611999 is 99911612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21611999 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 (21611939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10805999 + 10806000.

It is an arithmetic number, because the mean of its divisors is an integer number (10806000).

Almost surely, 2^21611999 is an apocalyptic number.

21611999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21611999 is an equidigital number, since it uses as much as digits as its factorization.

21611999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8748, while the sum is 38.

The square root of 21611999 is about 4648.8707230896. The cubic root of 21611999 is about 278.5468893822.

The spelling of 21611999 in words is "twenty-one million, six hundred eleven thousand, nine hundred ninety-nine".