21987696161 has 4 divisors (see below), whose sum is σ = 21995577024. Its totient is φ = 21979815300.

The previous prime is 21987696121. The next prime is 21987696169. The reversal of 21987696161 is 16169678912.

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 21987696161 - 2¹⁸ = 21987434017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21987696097 and 21987696106.

It is not an unprimeable number, because it can be changed into a prime (21987696169) 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, 3936245 + ... + 3941826.

It is an arithmetic number, because the mean of its divisors is an integer number (5498894256).

Almost surely, 2^21987696161 is an apocalyptic number.

It is an amenable number.

21987696161 is a deficient number, since it is larger than the sum of its proper divisors (7880863).

21987696161 is an equidigital number, since it uses as much as digits as its factorization.

21987696161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7880862.

The product of its digits is 1959552, while the sum is 56.

The spelling of 21987696161 in words is "twenty-one billion, nine hundred eighty-seven million, six hundred ninety-six thousand, one hundred sixty-one".