21987434 has 8 divisors (see below), whose sum is σ = 37692768. Its totient is φ = 9423180.

The previous prime is 21987403. The next prime is 21987461. The reversal of 21987434 is 43478912.

It is a sphenic number, since it is the product of 3 distinct primes.

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 3 ways as a sum of consecutive naturals, for example, 785252 + ... + 785279.

It is an arithmetic number, because the mean of its divisors is an integer number (4711596).

Almost surely, 2^21987434 is an apocalyptic number.

21987434 is a deficient number, since it is larger than the sum of its proper divisors (15705334).

21987434 is a wasteful number, since it uses less digits than its factorization.

21987434 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1570540.

The product of its digits is 48384, while the sum is 38.

The square root of 21987434 is about 4689.0760283877. The cubic root of 21987434 is about 280.1505737743.

The spelling of 21987434 in words is "twenty-one million, nine hundred eighty-seven thousand, four hundred thirty-four".