21226321665 has 24 divisors (see below), whose sum is σ = 36808556928. Its totient is φ = 11315700000.

The previous prime is 21226321663. The next prime is 21226321687. The reversal of 21226321665 is 56612362212.

21226321665 is a `hidden beast` number, since 2 + 1 + 2 + 2 + 632 + 16 + 6 + 5 = 666.

It is not a de Polignac number, because 21226321665 - 2¹ = 21226321663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21226321663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 211 + ... + 206040.

It is an arithmetic number, because the mean of its divisors is an integer number (1533689872).

Almost surely, 2^21226321665 is an apocalyptic number.

It is an amenable number.

21226321665 is a deficient number, since it is larger than the sum of its proper divisors (15582235263).

21226321665 is a wasteful number, since it uses less digits than its factorization.

21226321665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208549 (or 208546 counting only the distinct ones).

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

Adding to 21226321665 its reverse (56612362212), we get a palindrome (77838683877).

The spelling of 21226321665 in words is "twenty-one billion, two hundred twenty-six million, three hundred twenty-one thousand, six hundred sixty-five".