21144157 has 4 divisors (see below), whose sum is σ = 21362236. Its totient is φ = 20926080.

The previous prime is 21144121. The next prime is 21144173. The reversal of 21144157 is 75144112.

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 3663396 + 17480761 = 1914^2 + 4181^2 .

It is a cyclic number.

It is not a de Polignac number, because 21144157 - 2⁷ = 21144029 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 (21144187) 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, 108894 + ... + 109087.

It is an arithmetic number, because the mean of its divisors is an integer number (5340559).

Almost surely, 2^21144157 is an apocalyptic number.

It is an amenable number.

21144157 is a deficient number, since it is larger than the sum of its proper divisors (218079).

21144157 is an equidigital number, since it uses as much as digits as its factorization.

21144157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218078.

The product of its digits is 1120, while the sum is 25.

The square root of 21144157 is about 4598.2776123240. The cubic root of 21144157 is about 276.5222773619.

Adding to 21144157 its reverse (75144112), we get a palindrome (96288269).

The spelling of 21144157 in words is "twenty-one million, one hundred forty-four thousand, one hundred fifty-seven".