21655787 has 2 divisors, whose sum is σ = 21655788. Its totient is φ = 21655786.

The previous prime is 21655759. The next prime is 21655813. The reversal of 21655787 is 78755612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21655787 - 2⁶ = 21655723 is a prime.

It is a super-2 number, since 2×21655787² = 937946221178738, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21655087) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827893 + 10827894.

It is an arithmetic number, because the mean of its divisors is an integer number (10827894).

Almost surely, 2^21655787 is an apocalyptic number.

21655787 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655787 is an equidigital number, since it uses as much as digits as its factorization.

21655787 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 117600, while the sum is 41.

The square root of 21655787 is about 4653.5778708430. The cubic root of 21655787 is about 278.7348834530.

The spelling of 21655787 in words is "twenty-one million, six hundred fifty-five thousand, seven hundred eighty-seven".