21161666220 has 48 divisors (see below), whose sum is σ = 59308689888. Its totient is φ = 5637775360.

The previous prime is 21161666209. The next prime is 21161666269. The reversal of 21161666220 is 2266616112.

It is a super-2 number, since 2×21161666220² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 102549 + ... + 229868.

It is an arithmetic number, because the mean of its divisors is an integer number (1235597706).

Almost surely, 2^21161666220 is an apocalyptic number.

21161666220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21161666220 is an abundant number, since it is smaller than the sum of its proper divisors (38147023668).

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

21161666220 is a wasteful number, since it uses less digits than its factorization.

21161666220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333490 (or 333488 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The spelling of 21161666220 in words is "twenty-one billion, one hundred sixty-one million, six hundred sixty-six thousand, two hundred twenty".