400921 has 4 divisors (see below), whose sum is σ = 402192. Its totient is φ = 399652.

The previous prime is 400903. The next prime is 400927. The reversal of 400921 is 129004.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 400921 - 2⁹ = 400409 is a prime.

It is a Duffinian number.

400921 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 400895 and 400904.

It is not an unprimeable number, because it can be changed into a prime (400927) 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, 246 + ... + 928.

It is an arithmetic number, because the mean of its divisors is an integer number (100548).

2⁴⁰⁰⁹²¹ is an apocalyptic number.

It is an amenable number.

400921 is a deficient number, since it is larger than the sum of its proper divisors (1271).

400921 is an equidigital number, since it uses as much as digits as its factorization.

400921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1270.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 400921 is about 633.1832278259. The cubic root of 400921 is about 73.7371365097.

Adding to 400921 its reverse (129004), we get a palindrome (529925).

The spelling of 400921 in words is "four hundred thousand, nine hundred twenty-one".