21203121987 has 48 divisors (see below), whose sum is σ = 33881223168. Its totient is φ = 12730893120.

The previous prime is 21203121967. The next prime is 21203122009. The reversal of 21203121987 is 78912130212.

It is not a de Polignac number, because 21203121987 - 2¹⁴ = 21203105603 is a prime.

It is a super-4 number, since 4×21203121987⁴ (a number of 42 digits) contains 4444 as substring.

It is not an unprimeable number, because it can be changed into a prime (21203121967) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 192778 + ... + 282080.

It is an arithmetic number, because the mean of its divisors is an integer number (705858816).

Almost surely, 2^21203121987 is an apocalyptic number.

21203121987 is a deficient number, since it is larger than the sum of its proper divisors (12678101181).

21203121987 is a wasteful number, since it uses less digits than its factorization.

21203121987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89400 (or 89397 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The spelling of 21203121987 in words is "twenty-one billion, two hundred three million, one hundred twenty-one thousand, nine hundred eighty-seven".