20981811 has 4 divisors (see below), whose sum is σ = 27975752. Its totient is φ = 13987872.

The previous prime is 20981803. The next prime is 20981827. The reversal of 20981811 is 11818902.

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

It is not a de Polignac number, because 20981811 - 2³ = 20981803 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20981801) 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, 3496966 + ... + 3496971.

It is an arithmetic number, because the mean of its divisors is an integer number (6993938).

Almost surely, 2^20981811 is an apocalyptic number.

20981811 is a deficient number, since it is larger than the sum of its proper divisors (6993941).

20981811 is an equidigital number, since it uses as much as digits as its factorization.

20981811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6993940.

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 20981811 is about 4580.5906824339. The cubic root of 20981811 is about 275.8127405475.

The spelling of 20981811 in words is "twenty million, nine hundred eighty-one thousand, eight hundred eleven".