20640286440 has 48 divisors (see below), whose sum is σ = 67080932100. Its totient is φ = 5504076288.

The previous prime is 20640286439. The next prime is 20640286453. The reversal of 20640286440 is 4468204602.

It is a happy number.

20640286440 is a `hidden beast` number, since 2 + 0 + 6 + 4 + 0 + 2 + 8 + 644 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 20116883556 + 523402884 = 141834^2 + 22878^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 20640286395 and 20640286404.

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, 28666705 + ... + 28667424.

Almost surely, 2^20640286440 is an apocalyptic number.

20640286440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20640286440 is an abundant number, since it is smaller than the sum of its proper divisors (46440645660).

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

20640286440 is a wasteful number, since it uses less digits than its factorization.

20640286440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57334146 (or 57334139 counting only the distinct ones).

The product of its (nonzero) digits is 73728, while the sum is 36.

The spelling of 20640286440 in words is "twenty billion, six hundred forty million, two hundred eighty-six thousand, four hundred forty".