21906061 has 2 divisors, whose sum is σ = 21906062. Its totient is φ = 21906060.

The previous prime is 21906043. The next prime is 21906083. The reversal of 21906061 is 16060912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11055625 + 10850436 = 3325^2 + 3294^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21906061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21906041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953030 + 10953031.

It is an arithmetic number, because the mean of its divisors is an integer number (10953031).

Almost surely, 2^21906061 is an apocalyptic number.

It is an amenable number.

21906061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906061 is an equidigital number, since it uses as much as digits as its factorization.

21906061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 21906061 is about 4680.3911161355. The cubic root of 21906061 is about 279.8045447157.

Adding to 21906061 its reverse (16060912), we get a palindrome (37966973).

The spelling of 21906061 in words is "twenty-one million, nine hundred six thousand, sixty-one".