21123031885 has 8 divisors (see below), whose sum is σ = 25354509336. Its totient is φ = 16893844800.

The previous prime is 21123031883. The next prime is 21123031903. The reversal of 21123031885 is 58813032112.

It can be written as a sum of positive squares in 4 ways, for example, as 821911561 + 20301120324 = 28669^2 + 142482^2 .

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

It is not a de Polignac number, because 21123031885 - 2¹ = 21123031883 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21123031885.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123031883) 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 7 ways as a sum of consecutive naturals, for example, 552234 + ... + 589243.

It is an arithmetic number, because the mean of its divisors is an integer number (3169313667).

Almost surely, 2^21123031885 is an apocalyptic number.

It is an amenable number.

21123031885 is a deficient number, since it is larger than the sum of its proper divisors (4231477451).

21123031885 is a wasteful number, since it uses less digits than its factorization.

21123031885 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1145183.

The product of its (nonzero) digits is 11520, while the sum is 34.

Adding to 21123031885 its reverse (58813032112), we get a palindrome (79936063997).

The spelling of 21123031885 in words is "twenty-one billion, one hundred twenty-three million, thirty-one thousand, eight hundred eighty-five".