21671791 has 2 divisors, whose sum is σ = 21671792. Its totient is φ = 21671790.

The previous prime is 21671743. The next prime is 21671801. The reversal of 21671791 is 19717612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21671791 - 2¹³ = 21663599 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21671701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10835895 + 10835896.

It is an arithmetic number, because the mean of its divisors is an integer number (10835896).

Almost surely, 2^21671791 is an apocalyptic number.

21671791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21671791 is an equidigital number, since it uses as much as digits as its factorization.

21671791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5292, while the sum is 34.

The square root of 21671791 is about 4655.2970904122. The cubic root of 21671791 is about 278.8035298405.

The spelling of 21671791 in words is "twenty-one million, six hundred seventy-one thousand, seven hundred ninety-one".