43778221 has 2 divisors, whose sum is σ = 43778222. Its totient is φ = 43778220.

The previous prime is 43778219. The next prime is 43778227. The reversal of 43778221 is 12287734.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43705321 + 72900 = 6611^2 + 270^2 .

It is a cyclic number.

It is not a de Polignac number, because 43778221 - 2¹ = 43778219 is a prime.

Together with 43778219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (43778227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21889110 + 21889111.

It is an arithmetic number, because the mean of its divisors is an integer number (21889111).

Almost surely, 2^43778221 is an apocalyptic number.

It is an amenable number.

43778221 is a deficient number, since it is larger than the sum of its proper divisors (1).

43778221 is an equidigital number, since it uses as much as digits as its factorization.

43778221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18816, while the sum is 34.

The square root of 43778221 is about 6616.5112408278. The cubic root of 43778221 is about 352.4406848203.

The spelling of 43778221 in words is "forty-three million, seven hundred seventy-eight thousand, two hundred twenty-one".