21200640191 has 4 divisors (see below), whose sum is σ = 21222474984. Its totient is φ = 21178805400.

The previous prime is 21200640163. The next prime is 21200640203. The reversal of 21200640191 is 19104600212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21200640191 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21200640191.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21200640161) 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, 10915940 + ... + 10917881.

It is an arithmetic number, because the mean of its divisors is an integer number (5305618746).

Almost surely, 2^21200640191 is an apocalyptic number.

21200640191 is a deficient number, since it is larger than the sum of its proper divisors (21834793).

21200640191 is an equidigital number, since it uses as much as digits as its factorization.

21200640191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21834792.

The product of its (nonzero) digits is 864, while the sum is 26.

The spelling of 21200640191 in words is "twenty-one billion, two hundred million, six hundred forty thousand, one hundred ninety-one".