21787842 has 16 divisors (see below), whose sum is σ = 44589600. Its totient is φ = 7093632.

The previous prime is 21787819. The next prime is 21787853. The reversal of 21787842 is 24878712.

It is a self number, because there is not a number n which added to its sum of digits gives 21787842.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 41967 + ... + 42482.

It is an arithmetic number, because the mean of its divisors is an integer number (2786850).

Almost surely, 2^21787842 is an apocalyptic number.

21787842 is an abundant number, since it is smaller than the sum of its proper divisors (22801758).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21787842 is a wasteful number, since it uses less digits than its factorization.

21787842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84497.

The product of its digits is 50176, while the sum is 39.

The square root of 21787842 is about 4667.7448516387. The cubic root of 21787842 is about 279.3003022873.

The spelling of 21787842 in words is "twenty-one million, seven hundred eighty-seven thousand, eight hundred forty-two".