20021951 has 2 divisors, whose sum is σ = 20021952. Its totient is φ = 20021950.

The previous prime is 20021917. The next prime is 20021999. The reversal of 20021951 is 15912002.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20021951 - 2⁶ = 20021887 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20021251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10010975 + 10010976.

It is an arithmetic number, because the mean of its divisors is an integer number (10010976).

Almost surely, 2^20021951 is an apocalyptic number.

20021951 is a deficient number, since it is larger than the sum of its proper divisors (1).

20021951 is an equidigital number, since it uses as much as digits as its factorization.

20021951 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 20021951 is about 4474.5894783768. The cubic root of 20021951 is about 271.5410323187.

Adding to 20021951 its reverse (15912002), we get a palindrome (35933953).

The spelling of 20021951 in words is "twenty million, twenty-one thousand, nine hundred fifty-one".