42091821 has 12 divisors (see below), whose sum is σ = 63999520. Its totient is φ = 26584200.

The previous prime is 42091807. The next prime is 42091823. The reversal of 42091821 is 12819024.

It is not a de Polignac number, because 42091821 - 2¹⁸ = 41829677 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42091823) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 122905 + ... + 123246.

Almost surely, 2^42091821 is an apocalyptic number.

It is an amenable number.

42091821 is a deficient number, since it is larger than the sum of its proper divisors (21907699).

42091821 is a wasteful number, since it uses less digits than its factorization.

42091821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246176 (or 246173 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 42091821 is about 6487.8209747187. The cubic root of 42091821 is about 347.8557914185.

The spelling of 42091821 in words is "forty-two million, ninety-one thousand, eight hundred twenty-one".