21581991846909 has 96 divisors (see below), whose sum is σ = 35171677981440. Its totient is φ = 13145568371712.

The previous prime is 21581991846901. The next prime is 21581991846917. The reversal of 21581991846909 is 90964819918512.

It is a happy number.

21581991846909 is a `hidden beast` number, since 2 + 158 + 1 + 9 + 9 + 1 + 8 + 469 + 0 + 9 = 666.

It is an interprime number because it is at equal distance from previous prime (21581991846901) and next prime (21581991846917).

It is not a de Polignac number, because 21581991846909 - 2³ = 21581991846901 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21581991846901) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 332935669 + ... + 333000485.

It is an arithmetic number, because the mean of its divisors is an integer number (366371645640).

Almost surely, 2^{21581991846909} is an apocalyptic number.

It is an amenable number.

21581991846909 is a deficient number, since it is larger than the sum of its proper divisors (13589686134531).

21581991846909 is a wasteful number, since it uses less digits than its factorization.

21581991846909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65921 (or 65909 counting only the distinct ones).

The product of its (nonzero) digits is 100776960, while the sum is 72.

The spelling of 21581991846909 in words is "twenty-one trillion, five hundred eighty-one billion, nine hundred ninety-one million, eight hundred forty-six thousand, nine hundred nine".