21665101565602 has 12 divisors (see below), whose sum is σ = 35720560019718. Its totient is φ = 9847773438800.

The previous prime is 21665101565563. The next prime is 21665101565617. The reversal of 21665101565602 is 20656510156612.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 17178546379401 + 4486555186201 = 4144701^2 + 2118149^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 44762606299 + ... + 44762606782.

Almost surely, 2^{21665101565602} is an apocalyptic number.

21665101565602 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21665101565602 is a deficient number, since it is larger than the sum of its proper divisors (14055458454116).

21665101565602 is a wasteful number, since it uses less digits than its factorization.

21665101565602 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89525213105 (or 89525213094 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 46.

The spelling of 21665101565602 in words is "twenty-one trillion, six hundred sixty-five billion, one hundred one million, five hundred sixty-five thousand, six hundred two".