21166527391 has 8 divisors (see below), whose sum is σ = 21492293760. Its totient is φ = 20843130648.

The previous prime is 21166527379. The next prime is 21166527451. The reversal of 21166527391 is 19372566112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21166527391 - 2¹⁷ = 21166396319 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166527091) 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 7 ways as a sum of consecutive naturals, for example, 574401 + ... + 610138.

It is an arithmetic number, because the mean of its divisors is an integer number (2686536720).

Almost surely, 2^21166527391 is an apocalyptic number.

21166527391 is a deficient number, since it is larger than the sum of its proper divisors (325766369).

21166527391 is a wasteful number, since it uses less digits than its factorization.

21166527391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1184813.

The product of its digits is 136080, while the sum is 43.

The spelling of 21166527391 in words is "twenty-one billion, one hundred sixty-six million, five hundred twenty-seven thousand, three hundred ninety-one".