21761865 has 24 divisors (see below), whose sum is σ = 39119808. Its totient is φ = 11605680.

The previous prime is 21761863. The next prime is 21761867. The reversal of 21761865 is 56816712.

It is an interprime number because it is at equal distance from previous prime (21761863) and next prime (21761867).

It is not a de Polignac number, because 21761865 - 2¹ = 21761863 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21761863) 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 23 ways as a sum of consecutive naturals, for example, 7741 + ... + 10170.

It is an arithmetic number, because the mean of its divisors is an integer number (1629992).

Almost surely, 2^21761865 is an apocalyptic number.

It is an amenable number.

21761865 is a deficient number, since it is larger than the sum of its proper divisors (17357943).

21761865 is an equidigital number, since it uses as much as digits as its factorization.

21761865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17931 (or 17919 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21761865 is about 4664.9614146314. The cubic root of 21761865 is about 279.1892576456.

The spelling of 21761865 in words is "twenty-one million, seven hundred sixty-one thousand, eight hundred sixty-five".