21801400128 has 336 divisors, whose sum is σ = 69064632000. Its totient is φ = 6799085568.

The previous prime is 21801400099. The next prime is 21801400129. The reversal of 21801400128 is 82100410812.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21801400129) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 26298018 + ... + 26298846.

It is an arithmetic number, because the mean of its divisors is an integer number (205549500).

Almost surely, 2^21801400128 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 21801400128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34532316000).

21801400128 is an abundant number, since it is smaller than the sum of its proper divisors (47263231872).

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

21801400128 is an equidigital number, since it uses as much as digits as its factorization.

21801400128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 964 (or 942 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 27.

The spelling of 21801400128 in words is "twenty-one billion, eight hundred one million, four hundred thousand, one hundred twenty-eight".