721897993 has 4 divisors (see below), whose sum is σ = 721965060. Its totient is φ = 721830928.

The previous prime is 721897927. The next prime is 721898003. The reversal of 721897993 is 399798127.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 572740624 + 149157369 = 23932^2 + 12213^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721897993 is a prime.

It is a super-2 number, since 2×721897993² = 1042273424594856098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721897193) 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, 13330 + ... + 40267.

It is an arithmetic number, because the mean of its divisors is an integer number (180491265).

Almost surely, 2^721897993 is an apocalyptic number.

It is an amenable number.

721897993 is a deficient number, since it is larger than the sum of its proper divisors (67067).

721897993 is a wasteful number, since it uses less digits than its factorization.

721897993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67066.

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

The square root of 721897993 is about 26868.1594643176. The cubic root of 721897993 is about 897.0678207767.

The spelling of 721897993 in words is "seven hundred twenty-one million, eight hundred ninety-seven thousand, nine hundred ninety-three".