21101021993 has 8 divisors (see below), whose sum is σ = 21638402856. Its totient is φ = 20564723200.

The previous prime is 21101021987. The next prime is 21101022011. The reversal of 21101021993 is 39912010112.

It can be written as a sum of positive squares in 4 ways, for example, as 141800464 + 20959221529 = 11908^2 + 144773^2 .

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 21101021993 - 2³² = 16806054697 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21101021923) 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, 230948 + ... + 309093.

It is an arithmetic number, because the mean of its divisors is an integer number (2704800357).

Almost surely, 2^21101021993 is an apocalyptic number.

It is an amenable number.

21101021993 is a deficient number, since it is larger than the sum of its proper divisors (537380863).

21101021993 is an equidigital number, since it uses as much as digits as its factorization.

21101021993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 541035.

The product of its (nonzero) digits is 972, while the sum is 29.

The spelling of 21101021993 in words is "twenty-one billion, one hundred one million, twenty-one thousand, nine hundred ninety-three".