2021721621 has 8 divisors (see below), whose sum is σ = 2698755840. Its totient is φ = 1346250912.

The previous prime is 2021721607. The next prime is 2021721629. The reversal of 2021721621 is 1261271202.

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

It is not a de Polignac number, because 2021721621 - 2⁶ = 2021721557 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2021721591 and 2021721600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2021721629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 387856 + ... + 393033.

It is an arithmetic number, because the mean of its divisors is an integer number (337344480).

Almost surely, 2^2021721621 is an apocalyptic number.

It is an amenable number.

2021721621 is a deficient number, since it is larger than the sum of its proper divisors (677034219).

2021721621 is an equidigital number, since it uses as much as digits as its factorization.

2021721621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 781755.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 2021721621 is about 44963.5588115532. The cubic root of 2021721621 is about 1264.4658904302.

Adding to 2021721621 its reverse (1261271202), we get a palindrome (3282992823).

The spelling of 2021721621 in words is "two billion, twenty-one million, seven hundred twenty-one thousand, six hundred twenty-one".