747647721 has 18 divisors (see below), whose sum is σ = 1084960058. Its totient is φ = 496123200.

The previous prime is 747647717. The next prime is 747647749. The reversal of 747647721 is 127746747.

It can be written as a sum of positive squares in only one way, i.e., 389075625 + 358572096 = 19725^2 + 18936^2 .

It is not a de Polignac number, because 747647721 - 2² = 747647717 is a prime.

It is a super-2 number, since 2×747647721² = 1117954229432987682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (747647711) 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 17 ways as a sum of consecutive naturals, for example, 621921 + ... + 623121.

Almost surely, 2^747647721 is an apocalyptic number.

It is an amenable number.

747647721 is a deficient number, since it is larger than the sum of its proper divisors (337312337).

747647721 is a wasteful number, since it uses less digits than its factorization.

747647721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1733 (or 1467 counting only the distinct ones).

The product of its digits is 460992, while the sum is 45.

The square root of 747647721 is about 27343.1476059359. The cubic root of 747647721 is about 907.6094406183.

The spelling of 747647721 in words is "seven hundred forty-seven million, six hundred forty-seven thousand, seven hundred twenty-one".