21681781541 has 16 divisors (see below), whose sum is σ = 25051812864. Its totient is φ = 18381026304.

The previous prime is 21681781529. The next prime is 21681781553. The reversal of 21681781541 is 14518718612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21681781529) and next prime (21681781553).

It is a cyclic number.

It is not a de Polignac number, because 21681781541 - 2⁶ = 21681781477 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21681781492 and 21681781501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681781591) 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 15 ways as a sum of consecutive naturals, for example, 187340 + ... + 280106.

It is an arithmetic number, because the mean of its divisors is an integer number (1565738304).

Almost surely, 2^21681781541 is an apocalyptic number.

It is an amenable number.

21681781541 is a deficient number, since it is larger than the sum of its proper divisors (3370031323).

21681781541 is a wasteful number, since it uses less digits than its factorization.

21681781541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93140.

The product of its digits is 107520, while the sum is 44.

The spelling of 21681781541 in words is "twenty-one billion, six hundred eighty-one million, seven hundred eighty-one thousand, five hundred forty-one".