21936981 has 8 divisors (see below), whose sum is σ = 31908384. Its totient is φ = 13295120.

The previous prime is 21936979. The next prime is 21936989. The reversal of 21936981 is 18963912.

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

It is a cyclic number.

It is not a de Polignac number, because 21936981 - 2¹ = 21936979 is a prime.

It is a super-2 number, since 2×21936981² = 962462270788722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21936989) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 332346 + ... + 332411.

It is an arithmetic number, because the mean of its divisors is an integer number (3988548).

Almost surely, 2^21936981 is an apocalyptic number.

It is an amenable number.

21936981 is a deficient number, since it is larger than the sum of its proper divisors (9971403).

21936981 is a wasteful number, since it uses less digits than its factorization.

21936981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 664771.

The product of its digits is 23328, while the sum is 39.

The square root of 21936981 is about 4683.6930941299. The cubic root of 21936981 is about 279.9361291390.

The spelling of 21936981 in words is "twenty-one million, nine hundred thirty-six thousand, nine hundred eighty-one".