28378421 has 2 divisors, whose sum is σ = 28378422. Its totient is φ = 28378420.

The previous prime is 28378411. The next prime is 28378507. The reversal of 28378421 is 12487382.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27144100 + 1234321 = 5210^2 + 1111^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28378421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28378411) 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, 14189210 + 14189211.

It is an arithmetic number, because the mean of its divisors is an integer number (14189211).

Almost surely, 2^28378421 is an apocalyptic number.

It is an amenable number.

28378421 is a deficient number, since it is larger than the sum of its proper divisors (1).

28378421 is an equidigital number, since it uses as much as digits as its factorization.

28378421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21504, while the sum is 35.

The square root of 28378421 is about 5327.1400394583. The cubic root of 28378421 is about 305.0207671965.

The spelling of 28378421 in words is "twenty-eight million, three hundred seventy-eight thousand, four hundred twenty-one".