21002020123 has 16 divisors (see below), whose sum is σ = 24097328640. Its totient is φ = 17930552256.

The previous prime is 21002020103. The next prime is 21002020163. The reversal of 21002020123 is 32102020012.

It is a cyclic number.

It is not a de Polignac number, because 21002020123 - 2²¹ = 20999922971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21002020103) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4379415 + ... + 4384207.

It is an arithmetic number, because the mean of its divisors is an integer number (1506083040).

Almost surely, 2^21002020123 is an apocalyptic number.

21002020123 is a deficient number, since it is larger than the sum of its proper divisors (3095308517).

21002020123 is a wasteful number, since it uses less digits than its factorization.

21002020123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7146.

The product of its (nonzero) digits is 48, while the sum is 13.

Adding to 21002020123 its reverse (32102020012), we get a palindrome (53104040135).

The spelling of 21002020123 in words is "twenty-one billion, two million, twenty thousand, one hundred twenty-three".