72161731 has 4 divisors (see below), whose sum is σ = 72471672. Its totient is φ = 71851792.

The previous prime is 72161723. The next prime is 72161737. The reversal of 72161731 is 13716127.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 72161731 - 2³ = 72161723 is a prime.

It is a super-2 number, since 2×72161731² = 10414630841832722, which contains 22 as substring.

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 72161731.

It is not an unprimeable number, because it can be changed into a prime (72161737) 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, 154621 + ... + 155086.

It is an arithmetic number, because the mean of its divisors is an integer number (18117918).

Almost surely, 2^72161731 is an apocalyptic number.

72161731 is a deficient number, since it is larger than the sum of its proper divisors (309941).

72161731 is a wasteful number, since it uses less digits than its factorization.

72161731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 309940.

The product of its digits is 1764, while the sum is 28.

The square root of 72161731 is about 8494.8061190353. The cubic root of 72161731 is about 416.3280261466.

Adding to 72161731 its reverse (13716127), we get a palindrome (85877858).

The spelling of 72161731 in words is "seventy-two million, one hundred sixty-one thousand, seven hundred thirty-one".