20531866 has 4 divisors (see below), whose sum is σ = 30797802. Its totient is φ = 10265932.

The previous prime is 20531839. The next prime is 20531867. The reversal of 20531866 is 66813502.

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

It can be written as a sum of positive squares in only one way, i.e., 10791225 + 9740641 = 3285^2 + 3121^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (20531867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5132965 + ... + 5132968.

Almost surely, 2^20531866 is an apocalyptic number.

20531866 is a deficient number, since it is larger than the sum of its proper divisors (10265936).

20531866 is a wasteful number, since it uses less digits than its factorization.

20531866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10265935.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 20531866 is about 4531.2102136184. The cubic root of 20531866 is about 273.8269193022.

The spelling of 20531866 in words is "twenty million, five hundred thirty-one thousand, eight hundred sixty-six".