21981078 has 32 divisors (see below), whose sum is σ = 55825920. Its totient is φ = 6280200.

The previous prime is 21981059. The next prime is 21981079. The reversal of 21981078 is 87018912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981079) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28698 + ... + 29453.

It is an arithmetic number, because the mean of its divisors is an integer number (1744560).

Almost surely, 2^21981078 is an apocalyptic number.

21981078 is an abundant number, since it is smaller than the sum of its proper divisors (33844842).

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

21981078 is a wasteful number, since it uses less digits than its factorization.

21981078 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58169 (or 58163 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 21981078 is about 4688.3982339388. The cubic root of 21981078 is about 280.1235764046.

The spelling of 21981078 in words is "twenty-one million, nine hundred eighty-one thousand, seventy-eight".