20722181 has 2 divisors, whose sum is σ = 20722182. Its totient is φ = 20722180.

The previous prime is 20722171. The next prime is 20722189. The reversal of 20722181 is 18122702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19802500 + 919681 = 4450^2 + 959^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20722181 is a prime.

It is a super-2 number, since 2×20722181² = 858817570793522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20722189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10361090 + 10361091.

It is an arithmetic number, because the mean of its divisors is an integer number (10361091).

Almost surely, 2^20722181 is an apocalyptic number.

It is an amenable number.

20722181 is a deficient number, since it is larger than the sum of its proper divisors (1).

20722181 is an equidigital number, since it uses as much as digits as its factorization.

20722181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 20722181 is about 4552.1622334886. The cubic root of 20722181 is about 274.6703753060.

Adding to 20722181 its reverse (18122702), we get a palindrome (38844883).

The spelling of 20722181 in words is "twenty million, seven hundred twenty-two thousand, one hundred eighty-one".