72109561 has 2 divisors, whose sum is σ = 72109562. Its totient is φ = 72109560.

The previous prime is 72109553. The next prime is 72109589. The reversal of 72109561 is 16590127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67568400 + 4541161 = 8220^2 + 2131^2 .

It is a cyclic number.

It is not a de Polignac number, because 72109561 - 2³ = 72109553 is a prime.

It is a super-2 number, since 2×72109561² = 10399577575225442, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (72109511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36054780 + 36054781.

It is an arithmetic number, because the mean of its divisors is an integer number (36054781).

Almost surely, 2^72109561 is an apocalyptic number.

It is an amenable number.

72109561 is a deficient number, since it is larger than the sum of its proper divisors (1).

72109561 is an equidigital number, since it uses as much as digits as its factorization.

72109561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3780, while the sum is 31.

The square root of 72109561 is about 8491.7348639721. The cubic root of 72109561 is about 416.2276725422.

Adding to 72109561 its reverse (16590127), we get a palindrome (88699688).

The spelling of 72109561 in words is "seventy-two million, one hundred nine thousand, five hundred sixty-one".