21002020221 has 24 divisors (see below), whose sum is σ = 34654226880. Its totient is φ = 11077986816.

The previous prime is 21002020219. The next prime is 21002020231. The reversal of 21002020221 is 12202020012.

It is not a de Polignac number, because 21002020221 - 2¹ = 21002020219 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21002020197 and 21002020206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002020231) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2955316 + ... + 2962413.

It is an arithmetic number, because the mean of its divisors is an integer number (1443926120).

Almost surely, 2^21002020221 is an apocalyptic number.

21002020221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21002020221 is a deficient number, since it is larger than the sum of its proper divisors (13652206659).

21002020221 is a wasteful number, since it uses less digits than its factorization.

21002020221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5917765 (or 5917752 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

Adding to 21002020221 its reverse (12202020012), we get a palindrome (33204040233).

The spelling of 21002020221 in words is "twenty-one billion, two million, twenty thousand, two hundred twenty-one".