21897213257556 has 768 divisors, whose sum is σ = 71494875217920. Its totient is φ = 5643039467520.

The previous prime is 21897213257537. The next prime is 21897213257653. The reversal of 21897213257556 is 65575231279812.

21897213257556 is a `hidden beast` number, since 2 + 1 + 8 + 9 + 7 + 2 + 1 + 3 + 2 + 575 + 56 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a junction number, because it is equal to n+sod(n) for n = 21897213257493 and 21897213257502.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 25670824026 + ... + 25670824878.

It is an arithmetic number, because the mean of its divisors is an integer number (93092285440).

Almost surely, 2^{21897213257556} is an apocalyptic number.

21897213257556 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21897213257556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35747437608960).

21897213257556 is an abundant number, since it is smaller than the sum of its proper divisors (49597661960364).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21897213257556 is a wasteful number, since it uses less digits than its factorization.

21897213257556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1301 (or 1293 counting only the distinct ones).

The product of its digits is 63504000, while the sum is 63.

The spelling of 21897213257556 in words is "twenty-one trillion, eight hundred ninety-seven billion, two hundred thirteen million, two hundred fifty-seven thousand, five hundred fifty-six".