21123155212 has 6 divisors (see below), whose sum is σ = 36965521628. Its totient is φ = 10561577604.

The previous prime is 21123155147. The next prime is 21123155237. The reversal of 21123155212 is 21255132112.

It is a happy number.

It is a super-2 number, since 2×21123155212² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2640394398 + ... + 2640394405.

Almost surely, 2^21123155212 is an apocalyptic number.

It is an amenable number.

21123155212 is a deficient number, since it is larger than the sum of its proper divisors (15842366416).

21123155212 is a wasteful number, since it uses less digits than its factorization.

21123155212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5280788807 (or 5280788805 counting only the distinct ones).

The product of its digits is 1200, while the sum is 25.

Adding to 21123155212 its reverse (21255132112), we get a palindrome (42378287324).

The spelling of 21123155212 in words is "twenty-one billion, one hundred twenty-three million, one hundred fifty-five thousand, two hundred twelve".