72130781 has 2 divisors, whose sum is σ = 72130782. Its totient is φ = 72130780.

The previous prime is 72130777. The next prime is 72130787. The reversal of 72130781 is 18703127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40208281 + 31922500 = 6341^2 + 5650^2 .

It is an emirp because it is prime and its reverse (18703127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72130781 - 2² = 72130777 is a prime.

It is a super-2 number, since 2×72130781² = 10405699135339922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72130787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36065390 + 36065391.

It is an arithmetic number, because the mean of its divisors is an integer number (36065391).

Almost surely, 2^72130781 is an apocalyptic number.

It is an amenable number.

72130781 is a deficient number, since it is larger than the sum of its proper divisors (1).

72130781 is an equidigital number, since it uses as much as digits as its factorization.

72130781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 72130781 is about 8492.9842222861. The cubic root of 72130781 is about 416.2684969250.

The spelling of 72130781 in words is "seventy-two million, one hundred thirty thousand, seven hundred eighty-one".