40021661 has 2 divisors, whose sum is σ = 40021662. Its totient is φ = 40021660.

The previous prime is 40021627. The next prime is 40021703. The reversal of 40021661 is 16612004.

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., 28153636 + 11868025 = 5306^2 + 3445^2 .

It is a cyclic number.

It is not a de Polignac number, because 40021661 - 2¹⁰ = 40020637 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (40021061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20010830 + 20010831.

It is an arithmetic number, because the mean of its divisors is an integer number (20010831).

Almost surely, 2^40021661 is an apocalyptic number.

It is an amenable number.

40021661 is a deficient number, since it is larger than the sum of its proper divisors (1).

40021661 is an equidigital number, since it uses as much as digits as its factorization.

40021661 is an evil number, because the sum of its binary digits is even.

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

The square root of 40021661 is about 6326.2675409755. The cubic root of 40021661 is about 342.0569111770.

Adding to 40021661 its reverse (16612004), we get a palindrome (56633665).

The spelling of 40021661 in words is "forty million, twenty-one thousand, six hundred sixty-one".