20021256866 has 16 divisors (see below), whose sum is σ = 32662252728. Its totient is φ = 9149088000.

The previous prime is 20021256851. The next prime is 20021256917. The reversal of 20021256866 is 66865212002.

It can be written as a sum of positive squares in 4 ways, for example, as 19521957841 + 499299025 = 139721^2 + 22345^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3809495 + ... + 3814746.

Almost surely, 2^20021256866 is an apocalyptic number.

20021256866 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

20021256866 is a deficient number, since it is larger than the sum of its proper divisors (12640995862).

20021256866 is a wasteful number, since it uses less digits than its factorization.

20021256866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7624357.

The product of its (nonzero) digits is 69120, while the sum is 38.

Adding to 20021256866 its reverse (66865212002), we get a palindrome (86886468868).

The spelling of 20021256866 in words is "twenty billion, twenty-one million, two hundred fifty-six thousand, eight hundred sixty-six".