21012506541 has 20 divisors (see below), whose sum is σ = 33803597212. Its totient is φ = 12930772608.

The previous prime is 21012506513. The next prime is 21012506551. The reversal of 21012506541 is 14560521012.

21012506541 is a `hidden beast` number, since 2 + 1 + 0 + 1 + 2 + 5 + 0 + 654 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 5600277225 + 15412229316 = 74835^2 + 124146^2 .

It is not a de Polignac number, because 21012506541 - 2⁶ = 21012506477 is a prime.

It is a super-2 number, since 2×21012506541² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

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 (21012506551) by changing a digit.

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 19 ways as a sum of consecutive naturals, for example, 9976396 + ... + 9978501.

Almost surely, 2^21012506541 is an apocalyptic number.

It is an amenable number.

21012506541 is a deficient number, since it is larger than the sum of its proper divisors (12791090671).

21012506541 is a wasteful number, since it uses less digits than its factorization.

21012506541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19954922 (or 19954913 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

The spelling of 21012506541 in words is "twenty-one billion, twelve million, five hundred six thousand, five hundred forty-one".