21109478400 has 198 divisors, whose sum is σ = 75582744302. Its totient is φ = 5629132800.

The previous prime is 21109478353. The next prime is 21109478443. The reversal of 21109478400 is 487490112.

It can be written as a sum of positive squares in 3 ways, for example, as 2368963584 + 18740514816 = 48672^2 + 136896^2 .

It is a super-2 number, since 2×21109478400² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 184590 + ... + 276210.

Almost surely, 2^21109478400 is an apocalyptic number.

21109478400 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 21109478400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37791372151).

21109478400 is an abundant number, since it is smaller than the sum of its proper divisors (54473265902).

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

21109478400 is a wasteful number, since it uses less digits than its factorization.

21109478400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91657 (or 91631 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The spelling of 21109478400 in words is "twenty-one billion, one hundred nine million, four hundred seventy-eight thousand, four hundred".