7720645 has 4 divisors (see below), whose sum is σ = 9264780. Its totient is φ = 6176512.

The previous prime is 7720639. The next prime is 7720649. The reversal of 7720645 is 5460277.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5460277 = 19 ⋅287383.

It can be written as a sum of positive squares in 2 ways, for example, as 4955076 + 2765569 = 2226^2 + 1663^2 .

It is a cyclic number.

It is not a de Polignac number, because 7720645 - 2³ = 7720637 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7720649) 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, 772060 + ... + 772069.

It is an arithmetic number, because the mean of its divisors is an integer number (2316195).

Almost surely, 2^7720645 is an apocalyptic number.

It is an amenable number.

7720645 is a deficient number, since it is larger than the sum of its proper divisors (1544135).

7720645 is a wasteful number, since it uses less digits than its factorization.

7720645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1544134.

The product of its (nonzero) digits is 11760, while the sum is 31.

The square root of 7720645 is about 2778.6048657555. The cubic root of 7720645 is about 197.6444064857.

The spelling of 7720645 in words is "seven million, seven hundred twenty thousand, six hundred forty-five".