21131223987 has 54 divisors (see below), whose sum is σ = 30532132036. Its totient is φ = 12998613760.

The previous prime is 21131223973. The next prime is 21131224039. The reversal of 21131223987 is 78932213112.

It is not a de Polignac number, because 21131223987 - 2¹⁰ = 21131222963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131223947) 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 53 ways as a sum of consecutive naturals, for example, 237429439 + ... + 237429527.

Almost surely, 2^21131223987 is an apocalyptic number.

21131223987 is a deficient number, since it is larger than the sum of its proper divisors (9400908049).

21131223987 is an frugal number, since it uses more digits than its factorization.

21131223987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309 (or 156 counting only the distinct ones).

The product of its digits is 36288, while the sum is 39.

The spelling of 21131223987 in words is "twenty-one billion, one hundred thirty-one million, two hundred twenty-three thousand, nine hundred eighty-seven".