1647721745 has 4 divisors (see below), whose sum is σ = 1977266100. Its totient is φ = 1318177392.

The previous prime is 1647721741. The next prime is 1647721759. The reversal of 1647721745 is 5471277461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 505890064 + 1141831681 = 22492^2 + 33791^2 .

It is a cyclic number.

It is not a de Polignac number, because 1647721745 - 2² = 1647721741 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1647721696 and 1647721705.

It is not an unprimeable number, because it can be changed into a prime (1647721741) 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, 164772170 + ... + 164772179.

It is an arithmetic number, because the mean of its divisors is an integer number (494316525).

Almost surely, 2^1647721745 is an apocalyptic number.

It is an amenable number.

1647721745 is a deficient number, since it is larger than the sum of its proper divisors (329544355).

1647721745 is an equidigital number, since it uses as much as digits as its factorization.

1647721745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329544354.

The product of its digits is 329280, while the sum is 44.

The square root of 1647721745 is about 40592.1389557141. The cubic root of 1647721745 is about 1181.1216341199.

The spelling of 1647721745 in words is "one billion, six hundred forty-seven million, seven hundred twenty-one thousand, seven hundred forty-five".