21164269581 has 36 divisors (see below), whose sum is σ = 38297260092. Its totient is φ = 11163567744.

The previous prime is 21164269543. The next prime is 21164269589. The reversal of 21164269581 is 18596246112.

21164269581 is a `hidden beast` number, since 2 + 1 + 1 + 6 + 4 + 2 + 69 + 581 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 922093956 + 20242175625 = 30366^2 + 142275^2 .

It is not a de Polignac number, because 21164269581 - 2⁷ = 21164269453 is a prime.

It is a super-2 number, since 2×21164269581² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164269589) 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 35 ways as a sum of consecutive naturals, for example, 1840096 + ... + 1851561.

Almost surely, 2^21164269581 is an apocalyptic number.

21164269581 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21164269581 is a deficient number, since it is larger than the sum of its proper divisors (17132990511).

21164269581 is a wasteful number, since it uses less digits than its factorization.

21164269581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3691690 (or 3691680 counting only the distinct ones).

The product of its digits is 207360, while the sum is 45.

The spelling of 21164269581 in words is "twenty-one billion, one hundred sixty-four million, two hundred sixty-nine thousand, five hundred eighty-one".