21000010400 has 144 divisors (see below), whose sum is σ = 51994031544. Its totient is φ = 8281620480.

The previous prime is 21000010391. The next prime is 21000010411. The reversal of 21000010400 is 401000012.

It can be written as a sum of positive squares in 12 ways, for example, as 22543504 + 20977466896 = 4748^2 + 144836^2 .

It is a Harshad number since it is a multiple of its sum of digits (8).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21062702 + ... + 21063698.

Almost surely, 2^21000010400 is an apocalyptic number.

21000010400 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 21000010400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25997015772).

21000010400 is an abundant number, since it is smaller than the sum of its proper divisors (30994021144).

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

21000010400 is a wasteful number, since it uses less digits than its factorization.

21000010400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1363 (or 1350 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 8.

Adding to 21000010400 its reverse (401000012), we get a palindrome (21401010412).

The spelling of 21000010400 in words is "twenty-one billion, ten thousand, four hundred".