21557638889472 has 256 divisors, whose sum is σ = 67817840947200. Its totient is φ = 5960631582720.

The previous prime is 21557638889461. The next prime is 21557638889473. The reversal of 21557638889472 is 27498883675512.

It is a tau number, because it is divible by the number of its divisors (256).

It is a junction number, because it is equal to n+sod(n) for n = 21557638889394 and 21557638889403.

It is not an unprimeable number, because it can be changed into a prime (21557638889473) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20826679 + ... + 21837257.

It is an arithmetic number, because the mean of its divisors is an integer number (264913441200).

Almost surely, 2^{21557638889472} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21557638889472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33908920473600).

21557638889472 is an abundant number, since it is smaller than the sum of its proper divisors (46260202057728).

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

21557638889472 is an equidigital number, since it uses as much as digits as its factorization.

21557638889472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1010650 (or 1010622 counting only the distinct ones).

The product of its digits is 1625702400, while the sum is 75.

The spelling of 21557638889472 in words is "twenty-one trillion, five hundred fifty-seven billion, six hundred thirty-eight million, eight hundred eighty-nine thousand, four hundred seventy-two".