21164661533 has 4 divisors (see below), whose sum is σ = 21656863008. Its totient is φ = 20672460060.

The previous prime is 21164661499. The next prime is 21164661559. The reversal of 21164661533 is 33516646112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21164661533 - 2¹⁶ = 21164595997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164664533) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 246100673 + ... + 246100758.

It is an arithmetic number, because the mean of its divisors is an integer number (5414215752).

Almost surely, 2^21164661533 is an apocalyptic number.

It is an amenable number.

21164661533 is a deficient number, since it is larger than the sum of its proper divisors (492201475).

21164661533 is an equidigital number, since it uses as much as digits as its factorization.

21164661533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 492201474.

The product of its digits is 77760, while the sum is 38.

The spelling of 21164661533 in words is "twenty-one billion, one hundred sixty-four million, six hundred sixty-one thousand, five hundred thirty-three".