21216031320645 has 48 divisors (see below), whose sum is σ = 42036170771712. Its totient is φ = 9696859557120.

The previous prime is 21216031320641. The next prime is 21216031320677. The reversal of 21216031320645 is 54602313061212.

21216031320645 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 6 + 0 + 3 + 1 + 3 + 2 + 0 + 645 = 666.

It is not a de Polignac number, because 21216031320645 - 2² = 21216031320641 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216031320641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4975801 + ... + 8196990.

It is an arithmetic number, because the mean of its divisors is an integer number (875753557744).

Almost surely, 2^{21216031320645} is an apocalyptic number.

It is an amenable number.

21216031320645 is a deficient number, since it is larger than the sum of its proper divisors (20820139451067).

21216031320645 is a wasteful number, since it uses less digits than its factorization.

21216031320645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13177922 (or 13177919 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

Adding to 21216031320645 its reverse (54602313061212), we get a palindrome (75818344381857).

The spelling of 21216031320645 in words is "twenty-one trillion, two hundred sixteen billion, thirty-one million, three hundred twenty thousand, six hundred forty-five".