7801561 has 4 divisors (see below), whose sum is σ = 8012452. Its totient is φ = 7590672.

The previous prime is 7801523. The next prime is 7801567. The reversal of 7801561 is 1651087.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1651087 = 61 ⋅27067.

It can be written as a sum of positive squares in 2 ways, for example, as 7371225 + 430336 = 2715^2 + 656^2 .

It is a cyclic number.

It is not a de Polignac number, because 7801561 - 2¹¹ = 7799513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7801567) 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 3 ways as a sum of consecutive naturals, for example, 105390 + ... + 105463.

It is an arithmetic number, because the mean of its divisors is an integer number (2003113).

Almost surely, 2^7801561 is an apocalyptic number.

It is an amenable number.

7801561 is a deficient number, since it is larger than the sum of its proper divisors (210891).

7801561 is a wasteful number, since it uses less digits than its factorization.

7801561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210890.

The product of its (nonzero) digits is 1680, while the sum is 28.

The square root of 7801561 is about 2793.1274586026. The cubic root of 7801561 is about 198.3324771440.

It can be divided in two parts, 7801 and 561, that multiplied together give a triangular number (4376361 = T₂₉₅₈).

The spelling of 7801561 in words is "seven million, eight hundred one thousand, five hundred sixty-one".