21381245191 has 4 divisors (see below), whose sum is σ = 21448694232. Its totient is φ = 21313796152.

The previous prime is 21381245189. The next prime is 21381245201. The reversal of 21381245191 is 19154218312.

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 21381245191 - 2¹ = 21381245189 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21381245191.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381245141) 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, 33724045 + ... + 33724678.

It is an arithmetic number, because the mean of its divisors is an integer number (5362173558).

Almost surely, 2^21381245191 is an apocalyptic number.

21381245191 is a deficient number, since it is larger than the sum of its proper divisors (67449041).

21381245191 is an equidigital number, since it uses as much as digits as its factorization.

21381245191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67449040.

The product of its digits is 17280, while the sum is 37.

The spelling of 21381245191 in words is "twenty-one billion, three hundred eighty-one million, two hundred forty-five thousand, one hundred ninety-one".