21406161564 has 18 divisors (see below), whose sum is σ = 54110019600. Its totient is φ = 7135387176.

The previous prime is 21406161547. The next prime is 21406161589. The reversal of 21406161564 is 46516160412.

21406161564 is a `hidden beast` number, since 21 + 4 + 0 + 616 + 15 + 6 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 594615599 = 21406161564 / (2 + 1 + 4 + 0 + 6 + 1 + 6 + 1 + 5 + 6 + 4).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 297307764 + ... + 297307835.

It is an arithmetic number, because the mean of its divisors is an integer number (3006112200).

Almost surely, 2^21406161564 is an apocalyptic number.

It is an amenable number.

21406161564 is an abundant number, since it is smaller than the sum of its proper divisors (32703858036).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21406161564 is a wasteful number, since it uses less digits than its factorization.

21406161564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 594615609 (or 594615604 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

It can be divided in two parts, 214061 and 61564, that added together give a square (275625 = 525²).

The spelling of 21406161564 in words is "twenty-one billion, four hundred six million, one hundred sixty-one thousand, five hundred sixty-four".