72135781 has 2 divisors, whose sum is σ = 72135782. Its totient is φ = 72135780.

The previous prime is 72135757. The next prime is 72135827. The reversal of 72135781 is 18753127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66683556 + 5452225 = 8166^2 + 2335^2 .

It is an emirp because it is prime and its reverse (18753127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72135781 - 2⁹ = 72135269 is a prime.

It is a super-2 number, since 2×72135781² = 10407141800959922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72130781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36067890 + 36067891.

It is an arithmetic number, because the mean of its divisors is an integer number (36067891).

Almost surely, 2^72135781 is an apocalyptic number.

It is an amenable number.

72135781 is a deficient number, since it is larger than the sum of its proper divisors (1).

72135781 is an equidigital number, since it uses as much as digits as its factorization.

72135781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11760, while the sum is 34.

The square root of 72135781 is about 8493.2785777931. The cubic root of 72135781 is about 416.2781150768.

The spelling of 72135781 in words is "seventy-two million, one hundred thirty-five thousand, seven hundred eighty-one".