21164545541 has 4 divisors (see below), whose sum is σ = 21165414732. Its totient is φ = 21163676352.

The previous prime is 21164545499. The next prime is 21164545547. The reversal of 21164545541 is 14554546112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7270972900 + 13893572641 = 85270^2 + 117871^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21164545541 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21164545495 and 21164545504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164545547) 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, 396986 + ... + 447131.

It is an arithmetic number, because the mean of its divisors is an integer number (5291353683).

Almost surely, 2^21164545541 is an apocalyptic number.

It is an amenable number.

21164545541 is a deficient number, since it is larger than the sum of its proper divisors (869191).

21164545541 is an equidigital number, since it uses as much as digits as its factorization.

21164545541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 869190.

The product of its digits is 96000, while the sum is 38.

The spelling of 21164545541 in words is "twenty-one billion, one hundred sixty-four million, five hundred forty-five thousand, five hundred forty-one".