421661 has 2 divisors, whose sum is σ = 421662. Its totient is φ = 421660.

The previous prime is 421657. The next prime is 421691. The reversal of 421661 is 166124.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 337561 + 84100 = 581^2 + 290^2 .

It is a cyclic number.

It is not a de Polignac number, because 421661 - 2² = 421657 is a prime.

It is a Chen prime.

It is equal to p₃₅₅₁₆ and since 421661 and 35516 have the same sum of digits, it is a Honaker prime.

It is a plaindrome in base 11.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (421621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 210830 + 210831.

It is an arithmetic number, because the mean of its divisors is an integer number (210831).

2⁴²¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

421661 is a deficient number, since it is larger than the sum of its proper divisors (1).

421661 is an equidigital number, since it uses as much as digits as its factorization.

421661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 20.

The square root of 421661 is about 649.3542946651. The cubic root of 421661 is about 74.9873163736.

Adding to 421661 its reverse (166124), we get a palindrome (587785).

The spelling of 421661 in words is "four hundred twenty-one thousand, six hundred sixty-one".