72154781 has 4 divisors (see below), whose sum is σ = 72237564. Its totient is φ = 72072000.

The previous prime is 72154777. The next prime is 72154807. The reversal of 72154781 is 18745127.

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

It can be written as a sum of positive squares in 2 ways, for example, as 45010681 + 27144100 = 6709^2 + 5210^2 .

It is a cyclic number.

It is not a de Polignac number, because 72154781 - 2² = 72154777 is a prime.

It is a super-2 number, since 2×72154781² = 10412624842315922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72154751) 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, 40070 + ... + 41831.

It is an arithmetic number, because the mean of its divisors is an integer number (18059391).

Almost surely, 2^72154781 is an apocalyptic number.

It is an amenable number.

72154781 is a deficient number, since it is larger than the sum of its proper divisors (82783).

72154781 is an equidigital number, since it uses as much as digits as its factorization.

72154781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82782.

The product of its digits is 15680, while the sum is 35.

The square root of 72154781 is about 8494.3970356936. The cubic root of 72154781 is about 416.3146600007.

The spelling of 72154781 in words is "seventy-two million, one hundred fifty-four thousand, seven hundred eighty-one".