72197981 has 2 divisors, whose sum is σ = 72197982. Its totient is φ = 72197980.

The previous prime is 72197947. The next prime is 72197999. The reversal of 72197981 is 18979127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63840100 + 8357881 = 7990^2 + 2891^2 .

It is an emirp because it is prime and its reverse (18979127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72197981 - 2¹⁸ = 71935837 is a prime.

It is a super-2 number, since 2×72197981² = 10425096920952722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72197911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36098990 + 36098991.

It is an arithmetic number, because the mean of its divisors is an integer number (36098991).

Almost surely, 2^72197981 is an apocalyptic number.

It is an amenable number.

72197981 is a deficient number, since it is larger than the sum of its proper divisors (1).

72197981 is an equidigital number, since it uses as much as digits as its factorization.

72197981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 63504, while the sum is 44.

The square root of 72197981 is about 8496.9395078463. The cubic root of 72197981 is about 416.3977277476.

The spelling of 72197981 in words is "seventy-two million, one hundred ninety-seven thousand, nine hundred eighty-one".