21216351120666 has 32 divisors (see below), whose sum is σ = 45784130642880. Its totient is φ = 6515625982464.

The previous prime is 21216351120617. The next prime is 21216351120667. The reversal of 21216351120666 is 66602115361212.

It is not an unprimeable number, because it can be changed into a prime (21216351120667) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 260001751 + ... + 260083338.

It is an arithmetic number, because the mean of its divisors is an integer number (1430754082590).

Almost surely, 2^{21216351120666} is an apocalyptic number.

21216351120666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21216351120666 is an abundant number, since it is smaller than the sum of its proper divisors (24567779522214).

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

21216351120666 is a wasteful number, since it uses less digits than its factorization.

21216351120666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 520085630.

The product of its (nonzero) digits is 155520, while the sum is 42.

Adding to 21216351120666 its reverse (66602115361212), we get a palindrome (87818466481878).

The spelling of 21216351120666 in words is "twenty-one trillion, two hundred sixteen billion, three hundred fifty-one million, one hundred twenty thousand, six hundred sixty-six".