21178003722661 has 4 divisors (see below), whose sum is σ = 21296316592800. Its totient is φ = 21059690852524.

The previous prime is 21178003722653. The next prime is 21178003722677. The reversal of 21178003722661 is 16622730087112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21178003722661 - 2³ = 21178003722653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21178003722461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 59156434801 + ... + 59156435158.

It is an arithmetic number, because the mean of its divisors is an integer number (5324079148200).

Almost surely, 2^{21178003722661} is an apocalyptic number.

It is an amenable number.

21178003722661 is a deficient number, since it is larger than the sum of its proper divisors (118312870139).

21178003722661 is a wasteful number, since it uses less digits than its factorization.

21178003722661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118312870138.

The product of its (nonzero) digits is 338688, while the sum is 46.

The spelling of 21178003722661 in words is "twenty-one trillion, one hundred seventy-eight billion, three million, seven hundred twenty-two thousand, six hundred sixty-one".