21421220321 has 4 divisors (see below), whose sum is σ = 21425107200. Its totient is φ = 21417333444.

The previous prime is 21421220239. The next prime is 21421220383. The reversal of 21421220321 is 12302212412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21421220321 - 2³⁴ = 4241351137 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21421220293 and 21421220302.

It is not an unprimeable number, because it can be changed into a prime (21421220921) 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, 1935161 + ... + 1946198.

It is an arithmetic number, because the mean of its divisors is an integer number (5356276800).

Almost surely, 2^21421220321 is an apocalyptic number.

It is an amenable number.

21421220321 is a deficient number, since it is larger than the sum of its proper divisors (3886879).

21421220321 is an equidigital number, since it uses as much as digits as its factorization.

21421220321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3886878.

The product of its (nonzero) digits is 384, while the sum is 20.

Adding to 21421220321 its reverse (12302212412), we get a palindrome (33723432733).

The spelling of 21421220321 in words is "twenty-one billion, four hundred twenty-one million, two hundred twenty thousand, three hundred twenty-one".