21168231660 has 48 divisors (see below), whose sum is σ = 65856722400. Its totient is φ = 5644861632.

The previous prime is 21168231593. The next prime is 21168231671. The reversal of 21168231660 is 6613286112.

It is a happy number.

It is a super-2 number, since 2×21168231660² (a number of 21 digits) contains 22 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19599675 + ... + 19600754.

It is an arithmetic number, because the mean of its divisors is an integer number (1372015050).

Almost surely, 2^21168231660 is an apocalyptic number.

21168231660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21168231660 is an abundant number, since it is smaller than the sum of its proper divisors (44688490740).

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

21168231660 is a wasteful number, since it uses less digits than its factorization.

21168231660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39200447 (or 39200439 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

It can be divided in two parts, 211682 and 31660, that added together give a palindrome (243342).

The spelling of 21168231660 in words is "twenty-one billion, one hundred sixty-eight million, two hundred thirty-one thousand, six hundred sixty".