18400400 has 60 divisors (see below), whose sum is σ = 44640372. Its totient is φ = 7288320.

The previous prime is 18400397. The next prime is 18400423. The reversal of 18400400 is 400481.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 13456 + 18386944 = 116^2 + 4288^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 62654 + ... + 62946.

Almost surely, 2^18400400 is an apocalyptic number.

18400400 is a gapful number since it is divisible by the number (10) 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 18400400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22320186).

18400400 is an abundant number, since it is smaller than the sum of its proper divisors (26239972).

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

18400400 is a wasteful number, since it uses less digits than its factorization.

18400400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468 (or 457 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 18400400 is about 4289.5687428925. The cubic root of 18400400 is about 264.0031373977.

Adding to 18400400 its reverse (400481), we get a palindrome (18800881).

The spelling of 18400400 in words is "eighteen million, four hundred thousand, four hundred".