21221191 has 8 divisors (see below), whose sum is σ = 21619584. Its totient is φ = 20826360.

The previous prime is 21221171. The next prime is 21221237. The reversal of 21221191 is 19112212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21221191 - 2⁷ = 21221063 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 (21221131) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13096 + ... + 14626.

It is an arithmetic number, because the mean of its divisors is an integer number (2702448).

Almost surely, 2^21221191 is an apocalyptic number.

21221191 is a deficient number, since it is larger than the sum of its proper divisors (398393).

21221191 is a wasteful number, since it uses less digits than its factorization.

21221191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1781.

The product of its digits is 72, while the sum is 19.

The square root of 21221191 is about 4606.6463940702. The cubic root of 21221191 is about 276.8576860223.

It can be divided in two parts, 21221 and 191, that added together give a palindrome (21412).

The spelling of 21221191 in words is "twenty-one million, two hundred twenty-one thousand, one hundred ninety-one".