20987644 has 6 divisors (see below), whose sum is σ = 36728384. Its totient is φ = 10493820.

The previous prime is 20987627. The next prime is 20987711. The reversal of 20987644 is 44678902.

It is a junction number, because it is equal to n+sod(n) for n = 20987597 and 20987606.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 2623452 + ... + 2623459.

Almost surely, 2^20987644 is an apocalyptic number.

It is an amenable number.

20987644 is a deficient number, since it is larger than the sum of its proper divisors (15740740).

20987644 is a wasteful number, since it uses less digits than its factorization.

20987644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5246915 (or 5246913 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 40.

The square root of 20987644 is about 4581.2273464651. The cubic root of 20987644 is about 275.8382970744.

The spelling of 20987644 in words is "twenty million, nine hundred eighty-seven thousand, six hundred forty-four".