21645120000 has 400 divisors, whose sum is σ = 82376281152. Its totient is φ = 4945920000.

The previous prime is 21645119983. The next prime is 21645120011. The reversal of 21645120000 is 2154612.

It is a tau number, because it is divible by the number of its divisors (400).

It is a super-2 number, since 2×21645120000² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 6718390 + ... + 6721610.

Almost surely, 2^21645120000 is an apocalyptic number.

21645120000 is a gapful number since it is divisible by the number (20) 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 21645120000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41188140576).

21645120000 is an abundant number, since it is smaller than the sum of its proper divisors (60731161152).

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

21645120000 is an frugal number, since it uses more digits than its factorization.

21645120000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3269 (or 3238 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

Adding to 21645120000 its reverse (2154612), we get a palindrome (21647274612).

The spelling of 21645120000 in words is "twenty-one billion, six hundred forty-five million, one hundred twenty thousand".