21942387 has 8 divisors (see below), whose sum is σ = 32507280. Its totient is φ = 14628240.

The previous prime is 21942379. The next prime is 21942457. The reversal of 21942387 is 78324912.

It is not a de Polignac number, because 21942387 - 2³ = 21942379 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21942317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 406314 + ... + 406367.

It is an arithmetic number, because the mean of its divisors is an integer number (4063410).

Almost surely, 2^21942387 is an apocalyptic number.

21942387 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21942387 is a deficient number, since it is larger than the sum of its proper divisors (10564893).

21942387 is an equidigital number, since it uses as much as digits as its factorization.

21942387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 812690 (or 812684 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21942387 is about 4684.2701672726. The cubic root of 21942387 is about 279.9591224339.

The spelling of 21942387 in words is "twenty-one million, nine hundred forty-two thousand, three hundred eighty-seven".