21981221528 has 16 divisors (see below), whose sum is σ = 47102617680. Its totient is φ = 9420523488.

The previous prime is 21981221519. The next prime is 21981221533. The reversal of 21981221528 is 82512218912.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 196260851 + ... + 196260962.

It is an arithmetic number, because the mean of its divisors is an integer number (2943913605).

Almost surely, 2^21981221528 is an apocalyptic number.

21981221528 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21981221528 is an abundant number, since it is smaller than the sum of its proper divisors (25121396152).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21981221528 is a wasteful number, since it uses less digits than its factorization.

21981221528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392521826 (or 392521822 counting only the distinct ones).

The product of its digits is 46080, while the sum is 41.

The spelling of 21981221528 in words is "twenty-one billion, nine hundred eighty-one million, two hundred twenty-one thousand, five hundred twenty-eight".