21240654666 has 64 divisors (see below), whose sum is σ = 53601924096. Its totient is φ = 5450572800.

The previous prime is 21240654647. The next prime is 21240654691. The reversal of 21240654666 is 66645604212.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 238615 + ... + 315306.

It is an arithmetic number, because the mean of its divisors is an integer number (837530064).

Almost surely, 2^21240654666 is an apocalyptic number.

21240654666 is an abundant number, since it is smaller than the sum of its proper divisors (32361269430).

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

21240654666 is a wasteful number, since it uses less digits than its factorization.

21240654666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 554027.

The product of its (nonzero) digits is 414720, while the sum is 42.

The spelling of 21240654666 in words is "twenty-one billion, two hundred forty million, six hundred fifty-four thousand, six hundred sixty-six".