21661030443065 has 32 divisors (see below), whose sum is σ = 28524028883616. Its totient is φ = 15692297287680.

The previous prime is 21661030443049. The next prime is 21661030443113. The reversal of 21661030443065 is 56034403016612.

It can be written as a sum of positive squares in 16 ways, for example, as 885639095056 + 20775391348009 = 941084^2 + 4558003^2 .

It is not a de Polignac number, because 21661030443065 - 2⁴ = 21661030443049 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 31286117 + ... + 31970973.

It is an arithmetic number, because the mean of its divisors is an integer number (891375902613).

Almost surely, 2^{21661030443065} is an apocalyptic number.

It is an amenable number.

21661030443065 is a deficient number, since it is larger than the sum of its proper divisors (6862998440551).

21661030443065 is a wasteful number, since it uses less digits than its factorization.

21661030443065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 694109.

The product of its (nonzero) digits is 311040, while the sum is 41.

Adding to 21661030443065 its reverse (56034403016612), we get a palindrome (77695433459677).

The spelling of 21661030443065 in words is "twenty-one trillion, six hundred sixty-one billion, thirty million, four hundred forty-three thousand, sixty-five".