21665546453 has 16 divisors (see below), whose sum is σ = 23273079984. Its totient is φ = 20096778240.

The previous prime is 21665546407. The next prime is 21665546459. The reversal of 21665546453 is 35464556612.

It can be written as a sum of positive squares in 8 ways, for example, as 4995379684 + 16670166769 = 70678^2 + 129113^2 .

It is a cyclic number.

It is not a de Polignac number, because 21665546453 - 2¹⁶ = 21665480917 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21665546398 and 21665546407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665546459) 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, 370151 + ... + 424667.

It is an arithmetic number, because the mean of its divisors is an integer number (1454567499).

Almost surely, 2^21665546453 is an apocalyptic number.

It is an amenable number.

21665546453 is a deficient number, since it is larger than the sum of its proper divisors (1607533531).

21665546453 is a wasteful number, since it uses less digits than its factorization.

21665546453 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54872.

The product of its digits is 2592000, while the sum is 47.

The spelling of 21665546453 in words is "twenty-one billion, six hundred sixty-five million, five hundred forty-six thousand, four hundred fifty-three".