721533997 has 8 divisors (see below), whose sum is σ = 738211320. Its totient is φ = 704970240.

The previous prime is 721533979. The next prime is 721534019. The reversal of 721533997 is 799335127.

It can be written as a sum of positive squares in 4 ways, for example, as 182412036 + 539121961 = 13506^2 + 23219^2 .

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 721533997 - 2²⁷ = 587316269 is a prime.

It is a super-2 number, since 2×721533997² = 1041222617653592018, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721533097) 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, 15472 + ... + 41017.

It is an arithmetic number, because the mean of its divisors is an integer number (92276415).

Almost surely, 2^721533997 is an apocalyptic number.

It is an amenable number.

721533997 is a deficient number, since it is larger than the sum of its proper divisors (16677323).

721533997 is a wasteful number, since it uses less digits than its factorization.

721533997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56783.

The product of its digits is 357210, while the sum is 46.

The square root of 721533997 is about 26861.3848675008. The cubic root of 721533997 is about 896.9170220037.

The spelling of 721533997 in words is "seven hundred twenty-one million, five hundred thirty-three thousand, nine hundred ninety-seven".