21665402642 has 8 divisors (see below), whose sum is σ = 34997958156. Its totient is φ = 9999416592.

The previous prime is 21665402623. The next prime is 21665402659. The reversal of 21665402642 is 24620456612.

It can be written as a sum of positive squares in 2 ways, for example, as 21574028161 + 91374481 = 146881^2 + 9559^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21665402596 and 21665402605.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 416642333 + ... + 416642384.

Almost surely, 2^21665402642 is an apocalyptic number.

21665402642 is a deficient number, since it is larger than the sum of its proper divisors (13332555514).

21665402642 is a wasteful number, since it uses less digits than its factorization.

21665402642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 833284732.

The product of its (nonzero) digits is 138240, while the sum is 38.

The spelling of 21665402642 in words is "twenty-one billion, six hundred sixty-five million, four hundred two thousand, six hundred forty-two".