21563976981 has 8 divisors (see below), whose sum is σ = 28753968544. Its totient is φ = 14374985040.

The previous prime is 21563976971. The next prime is 21563976989. The reversal of 21563976981 is 18967936512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21563976981 - 2⁵ = 21563976949 is a prime.

It is a super-2 number, since 2×21563976981² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21563976989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 198031 + ... + 286956.

It is an arithmetic number, because the mean of its divisors is an integer number (3594246068).

Almost surely, 2^21563976981 is an apocalyptic number.

It is an amenable number.

21563976981 is a deficient number, since it is larger than the sum of its proper divisors (7189991563).

21563976981 is a wasteful number, since it uses less digits than its factorization.

21563976981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499811.

The product of its digits is 4898880, while the sum is 57.

The spelling of 21563976981 in words is "twenty-one billion, five hundred sixty-three million, nine hundred seventy-six thousand, nine hundred eighty-one".