21185443664 has 80 divisors (see below), whose sum is σ = 51566270976. Its totient is φ = 8190998400.

The previous prime is 21185443663. The next prime is 21185443693. The reversal of 21185443664 is 46634458112.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21185443663) 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, 95759 + ... + 227025.

Almost surely, 2^21185443664 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 21185443664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25783135488).

21185443664 is an abundant number, since it is smaller than the sum of its proper divisors (30380827312).

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

21185443664 is a wasteful number, since it uses less digits than its factorization.

21185443664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131424 (or 131418 counting only the distinct ones).

The product of its digits is 552960, while the sum is 44.

The spelling of 21185443664 in words is "twenty-one billion, one hundred eighty-five million, four hundred forty-three thousand, six hundred sixty-four".