72345561 has 4 divisors (see below), whose sum is σ = 96460752. Its totient is φ = 48230372.

The previous prime is 72345541. The next prime is 72345563. The reversal of 72345561 is 16554327.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16554327 = 3 ⋅5518109.

It is a cyclic number.

It is not a de Polignac number, because 72345561 - 2⁵ = 72345529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (72345563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12057591 + ... + 12057596.

It is an arithmetic number, because the mean of its divisors is an integer number (24115188).

Almost surely, 2^72345561 is an apocalyptic number.

It is an amenable number.

72345561 is a deficient number, since it is larger than the sum of its proper divisors (24115191).

72345561 is a wasteful number, since it uses less digits than its factorization.

72345561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24115190.

The product of its digits is 25200, while the sum is 33.

The square root of 72345561 is about 8505.6193777996. The cubic root of 72345561 is about 416.6812543870.

Adding to 72345561 its reverse (16554327), we get a palindrome (88899888).

It can be divided in two parts, 72345 and 561, that multiplied together give a triangular number (40585545 = T₉₀₀₉).

The spelling of 72345561 in words is "seventy-two million, three hundred forty-five thousand, five hundred sixty-one".