21221535542065 has 16 divisors (see below), whose sum is σ = 25598197141200. Its totient is φ = 16888994906112.

The previous prime is 21221535542063. The next prime is 21221535542071. The reversal of 21221535542065 is 56024553512212.

It can be written as a sum of positive squares in 8 ways, for example, as 172736659456 + 21048798882609 = 415616^2 + 4587897^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221535542065 - 2¹ = 21221535542063 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21221535542063) 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, 79178601 + ... + 79446169.

It is an arithmetic number, because the mean of its divisors is an integer number (1599887321325).

Almost surely, 2^{21221535542065} is an apocalyptic number.

It is an amenable number.

21221535542065 is a deficient number, since it is larger than the sum of its proper divisors (4376661599135).

21221535542065 is a wasteful number, since it uses less digits than its factorization.

21221535542065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 349956.

The product of its (nonzero) digits is 720000, while the sum is 43.

The spelling of 21221535542065 in words is "twenty-one trillion, two hundred twenty-one billion, five hundred thirty-five million, five hundred forty-two thousand, sixty-five".