21002120120987 has 4 divisors (see below), whose sum is σ = 21002391834816. Its totient is φ = 21001848407160.

The previous prime is 21002120120951. The next prime is 21002120121007. The reversal of 21002120120987 is 78902102120012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21002120120987 - 2⁸ = 21002120120731 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002120120087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135740939 + ... + 135895572.

It is an arithmetic number, because the mean of its divisors is an integer number (5250597958704).

Almost surely, 2^{21002120120987} is an apocalyptic number.

21002120120987 is a deficient number, since it is larger than the sum of its proper divisors (271713829).

21002120120987 is an equidigital number, since it uses as much as digits as its factorization.

21002120120987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271713828.

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

Adding to 21002120120987 its reverse (78902102120012), we get a palindrome (99904222240999).

The spelling of 21002120120987 in words is "twenty-one trillion, two billion, one hundred twenty million, one hundred twenty thousand, nine hundred eighty-seven".