21018191 has 2 divisors, whose sum is σ = 21018192. Its totient is φ = 21018190.

The previous prime is 21018167. The next prime is 21018211. The reversal of 21018191 is 19181012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21018191 - 2¹⁰ = 21017167 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 (21018091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10509095 + 10509096.

It is an arithmetic number, because the mean of its divisors is an integer number (10509096).

Almost surely, 2^21018191 is an apocalyptic number.

21018191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21018191 is an equidigital number, since it uses as much as digits as its factorization.

21018191 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 21018191 is about 4584.5600661350. The cubic root of 21018191 is about 275.9720574876.

The spelling of 21018191 in words is "twenty-one million, eighteen thousand, one hundred ninety-one".