72878821 has 2 divisors, whose sum is σ = 72878822. Its totient is φ = 72878820.

The previous prime is 72878809. The next prime is 72878831. The reversal of 72878821 is 12887827.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72488196 + 390625 = 8514^2 + 625^2 .

It is an emirp because it is prime and its reverse (12887827) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72878821 - 2²³ = 64490213 is a prime.

It is a super-2 number, since 2×72878821² = 10622645100700082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72878801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36439410 + 36439411.

It is an arithmetic number, because the mean of its divisors is an integer number (36439411).

Almost surely, 2^72878821 is an apocalyptic number.

It is an amenable number.

72878821 is a deficient number, since it is larger than the sum of its proper divisors (1).

72878821 is an equidigital number, since it uses as much as digits as its factorization.

72878821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 100352, while the sum is 43.

The square root of 72878821 is about 8536.9093353508. The cubic root of 72878821 is about 417.7025366995.

The spelling of 72878821 in words is "seventy-two million, eight hundred seventy-eight thousand, eight hundred twenty-one".