72121751 has 4 divisors (see below), whose sum is σ = 77669592. Its totient is φ = 66573912.

The previous prime is 72121697. The next prime is 72121757. The reversal of 72121751 is 15712127.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72121751 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 72121751.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72121757) 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, 2773901 + ... + 2773926.

It is an arithmetic number, because the mean of its divisors is an integer number (19417398).

Almost surely, 2^72121751 is an apocalyptic number.

72121751 is a deficient number, since it is larger than the sum of its proper divisors (5547841).

72121751 is a wasteful number, since it uses less digits than its factorization.

72121751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5547840.

The product of its digits is 980, while the sum is 26.

The square root of 72121751 is about 8492.4525903887. The cubic root of 72121751 is about 416.2511254167.

Adding to 72121751 its reverse (15712127), we get a palindrome (87833878).

The spelling of 72121751 in words is "seventy-two million, one hundred twenty-one thousand, seven hundred fifty-one".