40000021 has 2 divisors, whose sum is σ = 40000022. Its totient is φ = 40000020.

The previous prime is 40000003. The next prime is 40000033. The reversal of 40000021 is 12000004.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37075921 + 2924100 = 6089^2 + 1710^2 .

It is a cyclic number.

It is not a de Polignac number, because 40000021 - 2¹¹ = 39997973 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 39999959 and 40000013.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (40000061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20000010 + 20000011.

It is an arithmetic number, because the mean of its divisors is an integer number (20000011).

Almost surely, 2^40000021 is an apocalyptic number.

It is an amenable number.

40000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

40000021 is an equidigital number, since it uses as much as digits as its factorization.

40000021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8, while the sum is 7.

The square root of 40000021 is about 6324.5569805323. The cubic root of 40000021 is about 341.9952491845.

Adding to 40000021 its reverse (12000004), we get a palindrome (52000025).

The spelling of 40000021 in words is "forty million, twenty-one", and thus it is an aban number and an uban number.