21870240066 has 24 divisors (see below), whose sum is σ = 47455955820. Its totient is φ = 7279243776.

The previous prime is 21870240047. The next prime is 21870240089. The reversal of 21870240066 is 66004207812.

It can be written as a sum of positive squares in 2 ways, for example, as 21514729041 + 355511025 = 146679^2 + 18855^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21870240066.

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, 890571 + ... + 914798.

Almost surely, 2^21870240066 is an apocalyptic number.

21870240066 is an abundant number, since it is smaller than the sum of its proper divisors (25585715754).

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

21870240066 is a wasteful number, since it uses less digits than its factorization.

21870240066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1806050 (or 1806047 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

Adding to 21870240066 its reverse (66004207812), we get a palindrome (87874447878).

The spelling of 21870240066 in words is "twenty-one billion, eight hundred seventy million, two hundred forty thousand, sixty-six".