400215421 has 4 divisors (see below), whose sum is σ = 411032092. Its totient is φ = 389398752.

The previous prime is 400215407. The next prime is 400215443. The reversal of 400215421 is 124512004.

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 259532100 + 140683321 = 16110^2 + 11861^2 .

It is a cyclic number.

It is not a de Polignac number, because 400215421 - 2²⁵ = 366660989 is a prime.

It is a super-3 number, since 3×400215421³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400215121) 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, 5408280 + ... + 5408353.

It is an arithmetic number, because the mean of its divisors is an integer number (102758023).

Almost surely, 2^400215421 is an apocalyptic number.

It is an amenable number.

400215421 is a deficient number, since it is larger than the sum of its proper divisors (10816671).

400215421 is a wasteful number, since it uses less digits than its factorization.

400215421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10816670.

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 400215421 is about 20005.3848000982. The cubic root of 400215421 is about 736.9385456154.

Adding to 400215421 its reverse (124512004), we get a palindrome (524727425).

The spelling of 400215421 in words is "four hundred million, two hundred fifteen thousand, four hundred twenty-one".