72215731 has 4 divisors (see below), whose sum is σ = 82532272. Its totient is φ = 61899192.

The previous prime is 72215729. The next prime is 72215753. The reversal of 72215731 is 13751227.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13751227 = 7 ⋅1964461.

It is a cyclic number.

It is not a de Polignac number, because 72215731 - 2¹ = 72215729 is a prime.

It is a super-3 number, since 3×72215731³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 72215731.

It is not an unprimeable number, because it can be changed into a prime (72215131) 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, 5158260 + ... + 5158273.

It is an arithmetic number, because the mean of its divisors is an integer number (20633068).

Almost surely, 2^72215731 is an apocalyptic number.

72215731 is a deficient number, since it is larger than the sum of its proper divisors (10316541).

72215731 is a wasteful number, since it uses less digits than its factorization.

72215731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10316540.

The product of its digits is 2940, while the sum is 28.

The square root of 72215731 is about 8497.9839373819. The cubic root of 72215731 is about 416.4318489882.

Adding to 72215731 its reverse (13751227), we get a palindrome (85966958).

The spelling of 72215731 in words is "seventy-two million, two hundred fifteen thousand, seven hundred thirty-one".