21157361 has 4 divisors (see below), whose sum is σ = 21455424. Its totient is φ = 20859300.

The previous prime is 21157351. The next prime is 21157369. The reversal of 21157361 is 16375112.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21157361 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21157361.

It is not an unprimeable number, because it can be changed into a prime (21157369) 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, 148925 + ... + 149066.

It is an arithmetic number, because the mean of its divisors is an integer number (5363856).

Almost surely, 2^21157361 is an apocalyptic number.

It is an amenable number.

21157361 is a deficient number, since it is larger than the sum of its proper divisors (298063).

21157361 is an equidigital number, since it uses as much as digits as its factorization.

21157361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 298062.

The product of its digits is 1260, while the sum is 26.

The square root of 21157361 is about 4599.7131432297. The cubic root of 21157361 is about 276.5798258119.

The spelling of 21157361 in words is "twenty-one million, one hundred fifty-seven thousand, three hundred sixty-one".