21840061 has 2 divisors, whose sum is σ = 21840062. Its totient is φ = 21840060.

The previous prime is 21840047. The next prime is 21840079. The reversal of 21840061 is 16004812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17799961 + 4040100 = 4219^2 + 2010^2 .

It is a cyclic number.

It is not a de Polignac number, because 21840061 - 2⁵ = 21840029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21840361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10920030 + 10920031.

It is an arithmetic number, because the mean of its divisors is an integer number (10920031).

Almost surely, 2^21840061 is an apocalyptic number.

It is an amenable number.

21840061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21840061 is an equidigital number, since it uses as much as digits as its factorization.

21840061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21840061 is about 4673.3351046121. The cubic root of 21840061 is about 279.5232576122.

Adding to 21840061 its reverse (16004812), we get a palindrome (37844873).

The spelling of 21840061 in words is "twenty-one million, eight hundred forty thousand, sixty-one".