21123031012 has 12 divisors (see below), whose sum is σ = 39139734060. Its totient is φ = 9940249856.

The previous prime is 21123031001. The next prime is 21123031057. The reversal of 21123031012 is 21013032112.

It can be written as a sum of positive squares in 2 ways, for example, as 15171834276 + 5951196736 = 123174^2 + 77144^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 155316337 + ... + 155316472.

It is an arithmetic number, because the mean of its divisors is an integer number (3261644505).

Almost surely, 2^21123031012 is an apocalyptic number.

It is an amenable number.

21123031012 is a deficient number, since it is larger than the sum of its proper divisors (18016703048).

21123031012 is a wasteful number, since it uses less digits than its factorization.

21123031012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310632830 (or 310632828 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21123031012 its reverse (21013032112), we get a palindrome (42136063124).

It can be divided in two parts, 211230 and 31012, that added together give a palindrome (242242).

The spelling of 21123031012 in words is "twenty-one billion, one hundred twenty-three million, thirty-one thousand, twelve".