21722081 has 2 divisors, whose sum is σ = 21722082. Its totient is φ = 21722080.

The previous prime is 21722069. The next prime is 21722093. The reversal of 21722081 is 18022712.

It is a balanced prime because it is at equal distance from previous prime (21722069) and next prime (21722093).

It can be written as a sum of positive squares in only one way, i.e., 11424400 + 10297681 = 3380^2 + 3209^2 .

It is a cyclic number.

It is not a de Polignac number, because 21722081 - 2⁶ = 21722017 is a prime.

It is a super-2 number, since 2×21722081² = 943697605941122, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21722011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861040 + 10861041.

It is an arithmetic number, because the mean of its divisors is an integer number (10861041).

Almost surely, 2^21722081 is an apocalyptic number.

It is an amenable number.

21722081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21722081 is an equidigital number, since it uses as much as digits as its factorization.

21722081 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 21722081 is about 4660.6953343895. The cubic root of 21722081 is about 279.0190203842.

Adding to 21722081 its reverse (18022712), we get a palindrome (39744793).

The spelling of 21722081 in words is "twenty-one million, seven hundred twenty-two thousand, eighty-one".