21623798857581 has 48 divisors (see below), whose sum is σ = 33369891375600. Its totient is φ = 13445575557120.

The previous prime is 21623798857501. The next prime is 21623798857589. The reversal of 21623798857581 is 18575889732612.

21623798857581 is a `hidden beast` number, since 2 + 1 + 6 + 2 + 37 + 9 + 8 + 8 + 5 + 7 + 581 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 3879190228356 + 17744608629225 = 1969566^2 + 4212435^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21623798857581 is a prime.

It is a super-3 number, since 3×21623798857581³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21623798857589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 107454345 + ... + 107655393.

It is an arithmetic number, because the mean of its divisors is an integer number (695206070325).

Almost surely, 2^{21623798857581} is an apocalyptic number.

It is an amenable number.

21623798857581 is a deficient number, since it is larger than the sum of its proper divisors (11746092518019).

21623798857581 is a wasteful number, since it uses less digits than its factorization.

21623798857581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207406 (or 207403 counting only the distinct ones).

The product of its digits is 406425600, while the sum is 72.

The spelling of 21623798857581 in words is "twenty-one trillion, six hundred twenty-three billion, seven hundred ninety-eight million, eight hundred fifty-seven thousand, five hundred eighty-one".