21797187 has 4 divisors (see below), whose sum is σ = 29062920. Its totient is φ = 14531456.

The previous prime is 21797159. The next prime is 21797189. The reversal of 21797187 is 78179712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21797187 - 2¹⁰ = 21796163 is a prime.

It is a super-2 number, since 2×21797187² = 950234722225938, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21797189) 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, 3632862 + ... + 3632867.

It is an arithmetic number, because the mean of its divisors is an integer number (7265730).

Almost surely, 2^21797187 is an apocalyptic number.

21797187 is a deficient number, since it is larger than the sum of its proper divisors (7265733).

21797187 is an equidigital number, since it uses as much as digits as its factorization.

21797187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7265732.

The product of its digits is 49392, while the sum is 42.

The square root of 21797187 is about 4668.7457630503. The cubic root of 21797187 is about 279.3402280443.

The spelling of 21797187 in words is "twenty-one million, seven hundred ninety-seven thousand, one hundred eighty-seven".