21013020221 has 4 divisors (see below), whose sum is σ = 22249080252. Its totient is φ = 19776960192.

The previous prime is 21013020211. The next prime is 21013020233. The reversal of 21013020221 is 12202031012.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15557572900 + 5455447321 = 124730^2 + 73861^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013020221 - 2⁶ = 21013020157 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21013020196 and 21013020205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013020211) 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, 618029990 + ... + 618030023.

It is an arithmetic number, because the mean of its divisors is an integer number (5562270063).

Almost surely, 2^21013020221 is an apocalyptic number.

It is an amenable number.

21013020221 is a deficient number, since it is larger than the sum of its proper divisors (1236060031).

21013020221 is a wasteful number, since it uses less digits than its factorization.

21013020221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236060030.

The product of its (nonzero) digits is 48, while the sum is 14.

Adding to 21013020221 its reverse (12202031012), we get a palindrome (33215051233).

The spelling of 21013020221 in words is "twenty-one billion, thirteen million, twenty thousand, two hundred twenty-one".