21670505661 has 16 divisors (see below), whose sum is σ = 33514586624. Its totient is φ = 12198322224.

The previous prime is 21670505653. The next prime is 21670505671. The reversal of 21670505661 is 16650507612.

It is not a de Polignac number, because 21670505661 - 2³ = 21670505653 is a prime.

It is a super-2 number, since 2×21670505661² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21670505671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7699555 + ... + 7702368.

It is an arithmetic number, because the mean of its divisors is an integer number (2094661664).

Almost surely, 2^21670505661 is an apocalyptic number.

21670505661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21670505661 is a deficient number, since it is larger than the sum of its proper divisors (11844080963).

21670505661 is a wasteful number, since it uses less digits than its factorization.

21670505661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15402000.

The product of its (nonzero) digits is 75600, while the sum is 39.

The spelling of 21670505661 in words is "twenty-one billion, six hundred seventy million, five hundred five thousand, six hundred sixty-one".