21531420666 has 48 divisors (see below), whose sum is σ = 54066849408. Its totient is φ = 6065186400.

The previous prime is 21531420637. The next prime is 21531420689. The reversal of 21531420666 is 66602413512.

It is a self number, because there is not a number n which added to its sum of digits gives 21531420666.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1194465 + ... + 1212356.

It is an arithmetic number, because the mean of its divisors is an integer number (1126392696).

Almost surely, 2^21531420666 is an apocalyptic number.

21531420666 is an abundant number, since it is smaller than the sum of its proper divisors (32535428742).

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

21531420666 is a wasteful number, since it uses less digits than its factorization.

21531420666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2406907 (or 2406904 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The spelling of 21531420666 in words is "twenty-one billion, five hundred thirty-one million, four hundred twenty thousand, six hundred sixty-six".