21002997665 has 8 divisors (see below), whose sum is σ = 27142335528. Its totient is φ = 15509905920.

The previous prime is 21002997661. The next prime is 21002997679. The reversal of 21002997665 is 56679920012.

It can be written as a sum of positive squares in 4 ways, for example, as 57093136 + 20945904529 = 7556^2 + 144727^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21002997665 - 2² = 21002997661 is a prime.

It is a super-2 number, since 2×21002997665² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002997661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161561456 + ... + 161561585.

It is an arithmetic number, because the mean of its divisors is an integer number (3392791941).

Almost surely, 2^21002997665 is an apocalyptic number.

It is an amenable number.

21002997665 is a deficient number, since it is larger than the sum of its proper divisors (6139337863).

21002997665 is a wasteful number, since it uses less digits than its factorization.

21002997665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323123059.

The product of its (nonzero) digits is 408240, while the sum is 47.

The spelling of 21002997665 in words is "twenty-one billion, two million, nine hundred ninety-seven thousand, six hundred sixty-five".