21213191 has 4 divisors (see below), whose sum is σ = 21380352. Its totient is φ = 21046032.

The previous prime is 21213187. The next prime is 21213193. The reversal of 21213191 is 19131212.

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 21213191 - 2² = 21213187 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213193) 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, 83390 + ... + 83643.

It is an arithmetic number, because the mean of its divisors is an integer number (5345088).

Almost surely, 2^21213191 is an apocalyptic number.

21213191 is a deficient number, since it is larger than the sum of its proper divisors (167161).

21213191 is a wasteful number, since it uses less digits than its factorization.

21213191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167160.

The product of its digits is 108, while the sum is 20.

The square root of 21213191 is about 4605.7780015976. The cubic root of 21213191 is about 276.8228915588.

The spelling of 21213191 in words is "twenty-one million, two hundred thirteen thousand, one hundred ninety-one".