721978993 has 8 divisors (see below), whose sum is σ = 753657408. Its totient is φ = 690324624.

The previous prime is 721978991. The next prime is 721979009. The reversal of 721978993 is 399879127.

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

It is a cyclic number.

It is not a de Polignac number, because 721978993 - 2¹ = 721978991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721978991) 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, 84546 + ... + 92692.

It is an arithmetic number, because the mean of its divisors is an integer number (94207176).

Almost surely, 2^721978993 is an apocalyptic number.

It is an amenable number.

721978993 is a deficient number, since it is larger than the sum of its proper divisors (31678415).

721978993 is a wasteful number, since it uses less digits than its factorization.

721978993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12023.

The product of its digits is 1714608, while the sum is 55.

The square root of 721978993 is about 26869.6667824519. Note that the first 3 decimals coincide. The cubic root of 721978993 is about 897.1013711198.

The spelling of 721978993 in words is "seven hundred twenty-one million, nine hundred seventy-eight thousand, nine hundred ninety-three".