42878021 has 2 divisors, whose sum is σ = 42878022. Its totient is φ = 42878020.

The previous prime is 42877987. The next prime is 42878023. The reversal of 42878021 is 12087824.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 38613796 + 4264225 = 6214^2 + 2065^2 .

It is a cyclic number.

It is not a de Polignac number, because 42878021 - 2²² = 38683717 is a prime.

It is a Sophie Germain prime.

Together with 42878023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42878023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21439010 + 21439011.

It is an arithmetic number, because the mean of its divisors is an integer number (21439011).

Almost surely, 2^42878021 is an apocalyptic number.

It is an amenable number.

42878021 is a deficient number, since it is larger than the sum of its proper divisors (1).

42878021 is an equidigital number, since it uses as much as digits as its factorization.

42878021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7168, while the sum is 32.

The square root of 42878021 is about 6548.1311074229. The cubic root of 42878021 is about 350.0082202151.

The spelling of 42878021 in words is "forty-two million, eight hundred seventy-eight thousand, twenty-one".