21516406644 has 12 divisors (see below), whose sum is σ = 50204948864. Its totient is φ = 7172135544.

The previous prime is 21516406633. The next prime is 21516406657. The reversal of 21516406644 is 44660461512.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 896516932 + ... + 896516955.

Almost surely, 2^21516406644 is an apocalyptic number.

It is an amenable number.

21516406644 is an abundant number, since it is smaller than the sum of its proper divisors (28688542220).

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

21516406644 is a wasteful number, since it uses less digits than its factorization.

21516406644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1793033894 (or 1793033892 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 39.

The spelling of 21516406644 in words is "twenty-one billion, five hundred sixteen million, four hundred six thousand, six hundred forty-four".