402440021 has 4 divisors (see below), whose sum is σ = 407952972. Its totient is φ = 396927072.

The previous prime is 402439951. The next prime is 402440023. The reversal of 402440021 is 120044204.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 281769796 + 120670225 = 16786^2 + 10985^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-402440021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (402440023) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2756366 + ... + 2756511.

It is an arithmetic number, because the mean of its divisors is an integer number (101988243).

Almost surely, 2^402440021 is an apocalyptic number.

It is an amenable number.

402440021 is a deficient number, since it is larger than the sum of its proper divisors (5512951).

402440021 is an equidigital number, since it uses as much as digits as its factorization.

402440021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5512950.

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 402440021 is about 20060.9077810552. The cubic root of 402440021 is about 738.3014493765.

Adding to 402440021 its reverse (120044204), we get a palindrome (522484225).

The spelling of 402440021 in words is "four hundred two million, four hundred forty thousand, twenty-one".