42101821 has 2 divisors, whose sum is σ = 42101822. Its totient is φ = 42101820.

The previous prime is 42101803. The next prime is 42101827. The reversal of 42101821 is 12810124.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 31304025 + 10797796 = 5595^2 + 3286^2 .

It is a cyclic number.

It is not a de Polignac number, because 42101821 - 2⁵ = 42101789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42101827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21050910 + 21050911.

It is an arithmetic number, because the mean of its divisors is an integer number (21050911).

Almost surely, 2^42101821 is an apocalyptic number.

It is an amenable number.

42101821 is a deficient number, since it is larger than the sum of its proper divisors (1).

42101821 is an equidigital number, since it uses as much as digits as its factorization.

42101821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 42101821 is about 6488.5916037304. The cubic root of 42101821 is about 347.8833366153.

Adding to 42101821 its reverse (12810124), we get a palindrome (54911945).

The spelling of 42101821 in words is "forty-two million, one hundred one thousand, eight hundred twenty-one".