21613850645 has 4 divisors (see below), whose sum is σ = 25936620780. Its totient is φ = 17291080512.

The previous prime is 21613850641. The next prime is 21613850647. The reversal of 21613850645 is 54605831612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7902143236 + 13711707409 = 88894^2 + 117097^2 .

It is a cyclic number.

It is not a de Polignac number, because 21613850645 - 2² = 21613850641 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21613850641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2161385060 + ... + 2161385069.

It is an arithmetic number, because the mean of its divisors is an integer number (6484155195).

Almost surely, 2^21613850645 is an apocalyptic number.

It is an amenable number.

21613850645 is a deficient number, since it is larger than the sum of its proper divisors (4322770135).

21613850645 is an equidigital number, since it uses as much as digits as its factorization.

21613850645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4322770134.

The product of its (nonzero) digits is 172800, while the sum is 41.

The spelling of 21613850645 in words is "twenty-one billion, six hundred thirteen million, eight hundred fifty thousand, six hundred forty-five".