21171206440 has 16 divisors (see below), whose sum is σ = 47635214580. Its totient is φ = 8468482560.

The previous prime is 21171206431. The next prime is 21171206461. The reversal of 21171206440 is 4460217112.

It can be written as a sum of positive squares in 2 ways, for example, as 20243029284 + 928177156 = 142278^2 + 30466^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21171206399 and 21171206408.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264640041 + ... + 264640120.

Almost surely, 2^21171206440 is an apocalyptic number.

21171206440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21171206440 is an abundant number, since it is smaller than the sum of its proper divisors (26464008140).

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

21171206440 is a wasteful number, since it uses less digits than its factorization.

21171206440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 529280172 (or 529280168 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The spelling of 21171206440 in words is "twenty-one billion, one hundred seventy-one million, two hundred six thousand, four hundred forty".