1645421 has 2 divisors, whose sum is σ = 1645422.
Its totient is φ = 1645420.
The previous prime is 1645417. The next prime is 1645429. The reversal of 1645421 is 1245461.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 1297321 + 348100 = 1139^2 + 590^2
It is a cyclic number.
It is not a de Polignac number, because 1645421 - 22 = 1645417 is a prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (1645429) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822710 + 822711.
It is an arithmetic number, because the mean of its divisors is an integer number (822711).
21645421 is an apocalyptic number.
It is an amenable number.
1645421 is a deficient number, since it is larger than the sum of its proper divisors (1).
1645421 is an equidigital number, since it uses as much as digits as its factorization.
1645421 is an evil number, because the sum of its binary digits is even.
The product of its digits is 960, while the sum is 23.
The square root of 1645421 is about 1282.7396462260.
The cubic root of 1645421 is about 118.0571637233.
Subtracting from 1645421 its product of digits (960), we obtain a palindrome (1644461).
The spelling of 1645421 in words is "one million, six hundred forty-five thousand, four hundred twenty-one".