21121210987 has 2 divisors, whose sum is σ = 21121210988. Its totient is φ = 21121210986.

The previous prime is 21121210973. The next prime is 21121211011. The reversal of 21121210987 is 78901212112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21121210987 - 2¹⁵ = 21121178219 is a prime.

It is a super-2 number, since 2×21121210987² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21121210087) 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 as a sum of consecutive naturals, namely, 10560605493 + 10560605494.

It is an arithmetic number, because the mean of its divisors is an integer number (10560605494).

Almost surely, 2^21121210987 is an apocalyptic number.

21121210987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121210987 is an equidigital number, since it uses as much as digits as its factorization.

21121210987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 34.

The spelling of 21121210987 in words is "twenty-one billion, one hundred twenty-one million, two hundred ten thousand, nine hundred eighty-seven".