21108167661 has 16 divisors (see below), whose sum is σ = 32173481600. Its totient is φ = 12058564608.

The previous prime is 21108167653. The next prime is 21108167671. The reversal of 21108167661 is 16676180112.

It is not a de Polignac number, because 21108167661 - 2³ = 21108167653 is a prime.

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 (21108167671) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54196 + ... + 212493.

It is an arithmetic number, because the mean of its divisors is an integer number (2010842600).

Almost surely, 2^21108167661 is an apocalyptic number.

21108167661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21108167661 is a deficient number, since it is larger than the sum of its proper divisors (11065313939).

21108167661 is a wasteful number, since it uses less digits than its factorization.

21108167661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 270468.

The product of its (nonzero) digits is 24192, while the sum is 39.

The spelling of 21108167661 in words is "twenty-one billion, one hundred eight million, one hundred sixty-seven thousand, six hundred sixty-one".