21801943 has 2 divisors, whose sum is σ = 21801944. Its totient is φ = 21801942.

The previous prime is 21801931. The next prime is 21802009. The reversal of 21801943 is 34910812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21801943 - 2¹⁷ = 21670871 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21801443) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900971 + 10900972.

It is an arithmetic number, because the mean of its divisors is an integer number (10900972).

Almost surely, 2^21801943 is an apocalyptic number.

21801943 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801943 is an equidigital number, since it uses as much as digits as its factorization.

21801943 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21801943 is about 4669.2550797745. The cubic root of 21801943 is about 279.3605432881.

The spelling of 21801943 in words is "twenty-one million, eight hundred one thousand, nine hundred forty-three".