21002120545021 has 16 divisors (see below), whose sum is σ = 26184854683008. Its totient is φ = 16365043296000.

The previous prime is 21002120545009. The next prime is 21002120545031. The reversal of 21002120545021 is 12054502120012.

It is not a de Polignac number, because 21002120545021 - 2¹³ = 21002120536829 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002120545031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3209241 + ... + 7232113.

It is an arithmetic number, because the mean of its divisors is an integer number (1636553417688).

Almost surely, 2^{21002120545021} is an apocalyptic number.

It is an amenable number.

21002120545021 is a deficient number, since it is larger than the sum of its proper divisors (5182734137987).

21002120545021 is a wasteful number, since it uses less digits than its factorization.

21002120545021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4090692.

The product of its (nonzero) digits is 1600, while the sum is 25.

Adding to 21002120545021 its reverse (12054502120012), we get a palindrome (33056622665033).

The spelling of 21002120545021 in words is "twenty-one trillion, two billion, one hundred twenty million, five hundred forty-five thousand, twenty-one".