21989387 has 8 divisors (see below), whose sum is σ = 25644000. Its totient is φ = 18847752.

The previous prime is 21989377. The next prime is 21989389. The reversal of 21989387 is 78398912.

It is not a de Polignac number, because 21989387 - 2⁴ = 21989371 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21989389) by changing a digit.

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, 31712 + ... + 32397.

It is an arithmetic number, because the mean of its divisors is an integer number (3205500).

Almost surely, 2^21989387 is an apocalyptic number.

21989387 is a deficient number, since it is larger than the sum of its proper divisors (3654613).

21989387 is an frugal number, since it uses more digits than its factorization.

21989387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64130 (or 64116 counting only the distinct ones).

The product of its digits is 217728, while the sum is 47.

The square root of 21989387 is about 4689.2842737458. The cubic root of 21989387 is about 280.1588681767.

The spelling of 21989387 in words is "twenty-one million, nine hundred eighty-nine thousand, three hundred eighty-seven".