21212021987 has 6 divisors (see below), whose sum is σ = 22969231092. Its totient is φ = 19580327832.

The previous prime is 21212021959. The next prime is 21212022019. The reversal of 21212021987 is 78912021212.

It is not a de Polignac number, because 21212021987 - 2¹⁴ = 21212005603 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212021917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 62757293 + ... + 62757630.

It is an arithmetic number, because the mean of its divisors is an integer number (3828205182).

Almost surely, 2^21212021987 is an apocalyptic number.

21212021987 is a deficient number, since it is larger than the sum of its proper divisors (1757209105).

21212021987 is a wasteful number, since it uses less digits than its factorization.

21212021987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125514949 (or 125514936 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 35.

The spelling of 21212021987 in words is "twenty-one billion, two hundred twelve million, twenty-one thousand, nine hundred eighty-seven".