21531201191 has 2 divisors, whose sum is σ = 21531201192. Its totient is φ = 21531201190.

The previous prime is 21531201173. The next prime is 21531201221. The reversal of 21531201191 is 19110213512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21531201191 - 2¹⁸ = 21530939047 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21531201191.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21531201121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765600595 + 10765600596.

It is an arithmetic number, because the mean of its divisors is an integer number (10765600596).

Almost surely, 2^21531201191 is an apocalyptic number.

21531201191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531201191 is an equidigital number, since it uses as much as digits as its factorization.

21531201191 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 540, while the sum is 26.

The spelling of 21531201191 in words is "twenty-one billion, five hundred thirty-one million, two hundred one thousand, one hundred ninety-one".