21378856191 has 16 divisors (see below), whose sum is σ = 35538878208. Its totient is φ = 11105899200.

The previous prime is 21378856189. The next prime is 21378856193. The reversal of 21378856191 is 19165887312.

It is an interprime number because it is at equal distance from previous prime (21378856189) and next prime (21378856193).

It is not a de Polignac number, because 21378856191 - 2¹ = 21378856189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378856193) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46274350 + ... + 46274811.

It is an arithmetic number, because the mean of its divisors is an integer number (2221179888).

Almost surely, 2^21378856191 is an apocalyptic number.

21378856191 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21378856191 is a deficient number, since it is larger than the sum of its proper divisors (14160022017).

21378856191 is a wasteful number, since it uses less digits than its factorization.

21378856191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92549182.

The product of its digits is 725760, while the sum is 51.

The spelling of 21378856191 in words is "twenty-one billion, three hundred seventy-eight million, eight hundred fifty-six thousand, one hundred ninety-one".