21500100400 has 60 divisors (see below), whose sum is σ = 51800659992. Its totient is φ = 8575621120.

The previous prime is 21500100371. The next prime is 21500100403. The reversal of 21500100400 is 400100512.

It is not an unprimeable number, because it can be changed into a prime (21500100403) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 65067 + ... + 217333.

Almost surely, 2^21500100400 is an apocalyptic number.

21500100400 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 21500100400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25900329996).

21500100400 is an abundant number, since it is smaller than the sum of its proper divisors (30300559592).

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

21500100400 is a wasteful number, since it uses less digits than its factorization.

21500100400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152638 (or 152627 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

Adding to 21500100400 its reverse (400100512), we get a palindrome (21900200912).

The spelling of 21500100400 in words is "twenty-one billion, five hundred million, one hundred thousand, four hundred".