21039721663 has 8 divisors (see below), whose sum is σ = 21795056640. Its totient is φ = 20295918720.

The previous prime is 21039721643. The next prime is 21039721667. The reversal of 21039721663 is 36612793012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21039721663 - 2⁹ = 21039721151 is a prime.

It is a super-2 number, since 2×21039721663² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039721667) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2879295 + ... + 2886592.

It is an arithmetic number, because the mean of its divisors is an integer number (2724382080).

Almost surely, 2^21039721663 is an apocalyptic number.

21039721663 is a deficient number, since it is larger than the sum of its proper divisors (755334977).

21039721663 is an equidigital number, since it uses as much as digits as its factorization.

21039721663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5766017.

The product of its (nonzero) digits is 81648, while the sum is 40.

The spelling of 21039721663 in words is "twenty-one billion, thirty-nine million, seven hundred twenty-one thousand, six hundred sixty-three".