20400816 has 80 divisors (see below), whose sum is σ = 58281984. Its totient is φ = 6116352.

The previous prime is 20400811. The next prime is 20400823. The reversal of 20400816 is 61800402.

It is a junction number, because it is equal to n+sod(n) for n = 20400792 and 20400801.

It is not an unprimeable number, because it can be changed into a prime (20400811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18225 + ... + 19311.

Almost surely, 2^20400816 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20400816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29140992).

20400816 is an abundant number, since it is smaller than the sum of its proper divisors (37881168).

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

20400816 is a wasteful number, since it uses less digits than its factorization.

20400816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1138 (or 1132 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 20400816 is about 4516.7262480695. The cubic root of 20400816 is about 273.2430847534.

It can be divided in two parts, 20400 and 816, that multiplied together give a square (16646400 = 4080²).

The spelling of 20400816 in words is "twenty million, four hundred thousand, eight hundred sixteen".