20400400 has 30 divisors (see below), whose sum is σ = 49012922. Its totient is φ = 8160000.

The previous prime is 20400377. The next prime is 20400421. The reversal of 20400400 is 400402.

It can be written as a sum of positive squares in 3 ways, for example, as 3326976 + 17073424 = 1824^2 + 4132^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 25101 + ... + 25900.

Almost surely, 2^20400400 is an apocalyptic number.

20400400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20400400 is an abundant number, since it is smaller than the sum of its proper divisors (28612522).

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

20400400 is a wasteful number, since it uses less digits than its factorization.

20400400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51019 (or 51008 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 10.

The square root of 20400400 is about 4516.6801967817. The cubic root of 20400400 is about 273.2412274765.

Adding to 20400400 its reverse (400402), we get a palindrome (20800802).

The spelling of 20400400 in words is "twenty million, four hundred thousand, four hundred".