21202120191 has 32 divisors (see below), whose sum is σ = 33554956288. Its totient is φ = 11652685920.

The previous prime is 21202120187. The next prime is 21202120193. The reversal of 21202120191 is 19102120212.

It is not a de Polignac number, because 21202120191 - 2² = 21202120187 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21202120193) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6210 + ... + 206016.

It is an arithmetic number, because the mean of its divisors is an integer number (1048592384).

Almost surely, 2^21202120191 is an apocalyptic number.

21202120191 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21202120191 is a deficient number, since it is larger than the sum of its proper divisors (12352836097).

21202120191 is a wasteful number, since it uses less digits than its factorization.

21202120191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200011.

The product of its (nonzero) digits is 144, while the sum is 21.

Adding to 21202120191 its sum of digits (21), we get a palindrome (21202120212).

The spelling of 21202120191 in words is "twenty-one billion, two hundred two million, one hundred twenty thousand, one hundred ninety-one".