721973446921 has 4 divisors (see below), whose sum is σ = 723255815952. Its totient is φ = 720691077892.

The previous prime is 721973446861. The next prime is 721973446927. The reversal of 721973446921 is 129644379127.

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 721973446921 - 2⁷ = 721973446793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721973446927) 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, 641183671 + ... + 641184796.

It is an arithmetic number, because the mean of its divisors is an integer number (180813953988).

Almost surely, 2^721973446921 is an apocalyptic number.

It is an amenable number.

721973446921 is a deficient number, since it is larger than the sum of its proper divisors (1282369031).

721973446921 is a wasteful number, since it uses less digits than its factorization.

721973446921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1282369030.

The product of its digits is 4572288, while the sum is 55.

The spelling of 721973446921 in words is "seven hundred twenty-one billion, nine hundred seventy-three million, four hundred forty-six thousand, nine hundred twenty-one".