21281638628 has 24 divisors (see below), whose sum is σ = 38906282688. Its totient is φ = 10166609376.

The previous prime is 21281638621. The next prime is 21281638639. The reversal of 21281638628 is 82683618212.

It is not an unprimeable number, because it can be changed into a prime (21281638621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49751 + ... + 212222.

It is an arithmetic number, because the mean of its divisors is an integer number (1621095112).

Almost surely, 2^21281638628 is an apocalyptic number.

It is an amenable number.

21281638628 is a deficient number, since it is larger than the sum of its proper divisors (17624644060).

21281638628 is a wasteful number, since it uses less digits than its factorization.

21281638628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262883 (or 262881 counting only the distinct ones).

The product of its digits is 442368, while the sum is 47.

The spelling of 21281638628 in words is "twenty-one billion, two hundred eighty-one million, six hundred thirty-eight thousand, six hundred twenty-eight".