636391040 has 64 divisors (see below), whose sum is σ = 1546407720. Its totient is φ = 250368000.

The previous prime is 636391037. The next prime is 636391061. The reversal of 636391040 is 40193636.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 446392384 + 189998656 = 21128^2 + 13784^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 636390988 and 636391006.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30890 + ... + 47190.

Almost surely, 2^636391040 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 636391040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (773203860).

636391040 is an abundant number, since it is smaller than the sum of its proper divisors (910016680).

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

636391040 is a wasteful number, since it uses less digits than its factorization.

636391040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16381 (or 16369 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 32.

The square root of 636391040 is about 25226.7921068058. The cubic root of 636391040 is about 860.1509740356.

The spelling of 636391040 in words is "six hundred thirty-six million, three hundred ninety-one thousand, forty".