400021506 has 12 divisors (see below), whose sum is σ = 866713302. Its totient is φ = 133340496.

The previous prime is 400021471. The next prime is 400021507. The reversal of 400021506 is 605120004.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 374770881 + 25250625 = 19359^2 + 5025^2 .

It is a Harshad number since it is a multiple of its sum of digits (18), and also a Moran number because the ratio is a prime number: 22223417 = 400021506 / (4 + 0 + 0 + 0 + 2 + 1 + 5 + 0 + 6).

It is not an unprimeable number, because it can be changed into a prime (400021507) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 11111691 + ... + 11111726.

Almost surely, 2^400021506 is an apocalyptic number.

400021506 is an abundant number, since it is smaller than the sum of its proper divisors (466691796).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

400021506 is a wasteful number, since it uses less digits than its factorization.

400021506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22223425 (or 22223422 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 400021506 is about 20000.5376427735. The cubic root of 400021506 is about 736.8195042883.

The spelling of 400021506 in words is "four hundred million, twenty-one thousand, five hundred six".