21001420800 has 540 divisors, whose sum is σ = 78385479536. Its totient is φ = 5573836800.

The previous prime is 21001420787. The next prime is 21001420801. The reversal of 21001420800 is 802410012.

It is a tau number, because it is divible by the number of its divisors (540).

It is a super-3 number, since 3×21001420800³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21001420801) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 99532695 + ... + 99532905.

Almost surely, 2^21001420800 is an apocalyptic number.

21001420800 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 21001420800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39192739768).

21001420800 is an abundant number, since it is smaller than the sum of its proper divisors (57384058736).

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

21001420800 is an frugal number, since it uses more digits than its factorization.

21001420800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264 (or 221 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 21001420800 its reverse (802410012), we get a palindrome (21803830812).

The spelling of 21001420800 in words is "twenty-one billion, one million, four hundred twenty thousand, eight hundred".