21150421 has 4 divisors (see below), whose sum is σ = 21722092. Its totient is φ = 20578752.

The previous prime is 21150407. The next prime is 21150443. The reversal of 21150421 is 12405112.

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 19802500 + 1347921 = 4450^2 + 1161^2 .

It is a cyclic number.

It is not a de Polignac number, because 21150421 - 2⁷ = 21150293 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21150395 and 21150404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21150491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 285780 + ... + 285853.

It is an arithmetic number, because the mean of its divisors is an integer number (5430523).

Almost surely, 2^21150421 is an apocalyptic number.

It is an amenable number.

21150421 is a deficient number, since it is larger than the sum of its proper divisors (571671).

21150421 is an equidigital number, since it uses as much as digits as its factorization.

21150421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 571670.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21150421 is about 4598.9586864855. The cubic root of 21150421 is about 276.5495814303.

Adding to 21150421 its reverse (12405112), we get a palindrome (33555533).

It can be divided in two parts, 21 and 150421, that multiplied together give a triangular number (3158841 = T₂₅₁₃).

The spelling of 21150421 in words is "twenty-one million, one hundred fifty thousand, four hundred twenty-one".