21979756890 has 512 divisors, whose sum is σ = 76640256000. Its totient is φ = 4352818176.

The previous prime is 21979756853. The next prime is 21979756913. The reversal of 21979756890 is 9865797912.

It is a Harshad number since it is a multiple of its sum of digits (63).

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 255 ways as a sum of consecutive naturals, for example, 91965391 + ... + 91965629.

It is an arithmetic number, because the mean of its divisors is an integer number (149688000).

Almost surely, 2^21979756890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21979756890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38320128000).

21979756890 is an abundant number, since it is smaller than the sum of its proper divisors (54660499110).

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

21979756890 is a wasteful number, since it uses less digits than its factorization.

21979756890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 491 (or 485 counting only the distinct ones).

The product of its (nonzero) digits is 17146080, while the sum is 63.

The spelling of 21979756890 in words is "twenty-one billion, nine hundred seventy-nine million, seven hundred fifty-six thousand, eight hundred ninety".