21755915 has 8 divisors (see below), whose sum is σ = 26132208. Its totient is φ = 17388000.

The previous prime is 21755911. The next prime is 21755933. The reversal of 21755915 is 51955712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21755915 - 2² = 21755911 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21755911) 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 7 ways as a sum of consecutive naturals, for example, 8540 + ... + 10790.

It is an arithmetic number, because the mean of its divisors is an integer number (3266526).

Almost surely, 2^21755915 is an apocalyptic number.

21755915 is a deficient number, since it is larger than the sum of its proper divisors (4376293).

21755915 is a wasteful number, since it uses less digits than its factorization.

21755915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4189.

The product of its digits is 15750, while the sum is 35.

The square root of 21755915 is about 4664.3236379994. The cubic root of 21755915 is about 279.1638105695.

The spelling of 21755915 in words is "twenty-one million, seven hundred fifty-five thousand, nine hundred fifteen".