72978421 has 2 divisors, whose sum is σ = 72978422. Its totient is φ = 72978420.

The previous prime is 72978419. The next prime is 72978427. The reversal of 72978421 is 12487927.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67404100 + 5574321 = 8210^2 + 2361^2 .

It is an emirp because it is prime and its reverse (12487927) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72978421 - 2¹ = 72978419 is a prime.

Together with 72978419, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72978427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36489210 + 36489211.

It is an arithmetic number, because the mean of its divisors is an integer number (36489211).

Almost surely, 2^72978421 is an apocalyptic number.

It is an amenable number.

72978421 is a deficient number, since it is larger than the sum of its proper divisors (1).

72978421 is an equidigital number, since it uses as much as digits as its factorization.

72978421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56448, while the sum is 40.

The square root of 72978421 is about 8542.7408365231. The cubic root of 72978421 is about 417.8927347758.

The spelling of 72978421 in words is "seventy-two million, nine hundred seventy-eight thousand, four hundred twenty-one".