20021021191 has 4 divisors (see below), whose sum is σ = 20039272992. Its totient is φ = 20002769392.

The previous prime is 20021021177. The next prime is 20021021203. The reversal of 20021021191 is 19112012002.

It is a happy number.

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 20021021191 - 2¹¹ = 20021019143 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 (20021001191) 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, 9124255 + ... + 9126448.

It is an arithmetic number, because the mean of its divisors is an integer number (5009818248).

Almost surely, 2^20021021191 is an apocalyptic number.

20021021191 is a deficient number, since it is larger than the sum of its proper divisors (18251801).

20021021191 is a wasteful number, since it uses less digits than its factorization.

20021021191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18251800.

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

Adding to 20021021191 its reverse (19112012002), we get a palindrome (39133033193).

The spelling of 20021021191 in words is "twenty billion, twenty-one million, twenty-one thousand, one hundred ninety-one".