20981393 has 4 divisors (see below), whose sum is σ = 20995380. Its totient is φ = 20967408.

The previous prime is 20981371. The next prime is 20981399. The reversal of 20981393 is 39318902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2765569 + 18215824 = 1663^2 + 4268^2 .

It is a cyclic number.

It is not a de Polignac number, because 20981393 - 2¹⁶ = 20915857 is a prime.

It is a super-3 number, since 3×20981393³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20981399) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4430 + ... + 7847.

It is an arithmetic number, because the mean of its divisors is an integer number (5248845).

Almost surely, 2^20981393 is an apocalyptic number.

It is an amenable number.

20981393 is a deficient number, since it is larger than the sum of its proper divisors (13987).

20981393 is a wasteful number, since it uses less digits than its factorization.

20981393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13986.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 20981393 is about 4580.5450549034. The cubic root of 20981393 is about 275.8109089533.

The spelling of 20981393 in words is "twenty million, nine hundred eighty-one thousand, three hundred ninety-three".