21154213 has 4 divisors (see below), whose sum is σ = 21230860. Its totient is φ = 21077568.

The previous prime is 21154207. The next prime is 21154283. The reversal of 21154213 is 31245112.

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 4524129 + 16630084 = 2127^2 + 4078^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154213 - 2⁹ = 21153701 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 (21154283) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37908 + ... + 38461.

It is an arithmetic number, because the mean of its divisors is an integer number (5307715).

Almost surely, 2^21154213 is an apocalyptic number.

It is an amenable number.

21154213 is a deficient number, since it is larger than the sum of its proper divisors (76647).

21154213 is an equidigital number, since it uses as much as digits as its factorization.

21154213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76646.

The product of its digits is 240, while the sum is 19.

The square root of 21154213 is about 4599.3709352476. The cubic root of 21154213 is about 276.5661077104.

Adding to 21154213 its reverse (31245112), we get a palindrome (52399325).

It can be divided in two parts, 2115 and 4213, that added together give a triangular number (6328 = T₁₁₂).

The spelling of 21154213 in words is "twenty-one million, one hundred fifty-four thousand, two hundred thirteen".