21109081247 has 4 divisors (see below), whose sum is σ = 21111237840. Its totient is φ = 21106924656.

The previous prime is 21109081207. The next prime is 21109081267. The reversal of 21109081247 is 74218090112.

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 21109081247 - 2¹⁸ = 21108819103 is a prime.

It is a super-2 number, since 2×21109081247² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21109081207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1063547 + ... + 1083212.

It is an arithmetic number, because the mean of its divisors is an integer number (5277809460).

Almost surely, 2^21109081247 is an apocalyptic number.

21109081247 is a deficient number, since it is larger than the sum of its proper divisors (2156593).

21109081247 is an equidigital number, since it uses as much as digits as its factorization.

21109081247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2156592.

The product of its (nonzero) digits is 8064, while the sum is 35.

The spelling of 21109081247 in words is "twenty-one billion, one hundred nine million, eighty-one thousand, two hundred forty-seven".