42557621 has 2 divisors, whose sum is σ = 42557622. Its totient is φ = 42557620.

The previous prime is 42557617. The next prime is 42557623. The reversal of 42557621 is 12675524.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 35343025 + 7214596 = 5945^2 + 2686^2 .

It is a cyclic number.

It is not a de Polignac number, because 42557621 - 2² = 42557617 is a prime.

It is a super-2 number, since 2×42557621² = 3622302210359282, which contains 22 as substring.

Together with 42557623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42557623) 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, 21278810 + 21278811.

It is an arithmetic number, because the mean of its divisors is an integer number (21278811).

Almost surely, 2^42557621 is an apocalyptic number.

It is an amenable number.

42557621 is a deficient number, since it is larger than the sum of its proper divisors (1).

42557621 is an equidigital number, since it uses as much as digits as its factorization.

42557621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16800, while the sum is 32.

The square root of 42557621 is about 6523.6202372609. The cubic root of 42557621 is about 349.1342439147.

The spelling of 42557621 in words is "forty-two million, five hundred fifty-seven thousand, six hundred twenty-one".