21020420321 has 8 divisors (see below), whose sum is σ = 22259111040. Its totient is φ = 19781973568.

The previous prime is 21020420303. The next prime is 21020420327. The reversal of 21020420321 is 12302402012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21020420321 - 2³⁰ = 19946678497 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21020420321.

It is not an unprimeable number, because it can be changed into a prime (21020420327) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 134300 + ... + 245106.

It is an arithmetic number, because the mean of its divisors is an integer number (2782388880).

Almost surely, 2^21020420321 is an apocalyptic number.

It is an amenable number.

21020420321 is a deficient number, since it is larger than the sum of its proper divisors (1238690719).

21020420321 is a wasteful number, since it uses less digits than its factorization.

21020420321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121983.

The product of its (nonzero) digits is 192, while the sum is 17.

Adding to 21020420321 its reverse (12302402012), we get a palindrome (33322822333).

The spelling of 21020420321 in words is "twenty-one billion, twenty million, four hundred twenty thousand, three hundred twenty-one".