21191867 has 4 divisors (see below), whose sum is σ = 21490416. Its totient is φ = 20893320.

The previous prime is 21191857. The next prime is 21191873. The reversal of 21191867 is 76819112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21191867 - 2⁶ = 21191803 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21191857) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 149168 + ... + 149309.

It is an arithmetic number, because the mean of its divisors is an integer number (5372604).

Almost surely, 2^21191867 is an apocalyptic number.

21191867 is a deficient number, since it is larger than the sum of its proper divisors (298549).

21191867 is an equidigital number, since it uses as much as digits as its factorization.

21191867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298548.

The product of its digits is 6048, while the sum is 35.

The square root of 21191867 is about 4603.4625012049. The cubic root of 21191867 is about 276.7301041609.

The spelling of 21191867 in words is "twenty-one million, one hundred ninety-one thousand, eight hundred sixty-seven".