72071561 has 4 divisors (see below), whose sum is σ = 73253124. Its totient is φ = 70890000.

The previous prime is 72071557. The next prime is 72071599. The reversal of 72071561 is 16517027.

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 9265936 + 62805625 = 3044^2 + 7925^2 .

It is a cyclic number.

It is not a de Polignac number, because 72071561 - 2² = 72071557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72071501) 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, 590690 + ... + 590811.

It is an arithmetic number, because the mean of its divisors is an integer number (18313281).

Almost surely, 2^72071561 is an apocalyptic number.

It is an amenable number.

72071561 is a deficient number, since it is larger than the sum of its proper divisors (1181563).

72071561 is a wasteful number, since it uses less digits than its factorization.

72071561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1181562.

The product of its (nonzero) digits is 2940, while the sum is 29.

The square root of 72071561 is about 8489.4970993575. The cubic root of 72071561 is about 416.1545457128.

Adding to 72071561 its reverse (16517027), we get a palindrome (88588588).

The spelling of 72071561 in words is "seventy-two million, seventy-one thousand, five hundred sixty-one".