6921913621 has 4 divisors (see below), whose sum is σ = 7910758432. Its totient is φ = 5933068812.

The previous prime is 6921913619. The next prime is 6921913631. The reversal of 6921913621 is 1263191296.

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 6921913621 - 2¹ = 6921913619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6921913631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 494422395 + ... + 494422408.

It is an arithmetic number, because the mean of its divisors is an integer number (1977689608).

Almost surely, 2^6921913621 is an apocalyptic number.

It is an amenable number.

6921913621 is a deficient number, since it is larger than the sum of its proper divisors (988844811).

6921913621 is an equidigital number, since it uses as much as digits as its factorization.

6921913621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 988844810.

The product of its digits is 34992, while the sum is 40.

The square root of 6921913621 is about 83198.0385646200. The cubic root of 6921913621 is about 1905.7915271062.

The spelling of 6921913621 in words is "six billion, nine hundred twenty-one million, nine hundred thirteen thousand, six hundred twenty-one".