21791515 has 8 divisors (see below), whose sum is σ = 26176320. Its totient is φ = 17415552.

The previous prime is 21791509. The next prime is 21791519. The reversal of 21791515 is 51519712.

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

It is a cyclic number.

It is not a de Polignac number, because 21791515 - 2³ = 21791507 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21791519) 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 7 ways as a sum of consecutive naturals, for example, 5982 + ... + 8908.

It is an arithmetic number, because the mean of its divisors is an integer number (3272040).

Almost surely, 2^21791515 is an apocalyptic number.

21791515 is a deficient number, since it is larger than the sum of its proper divisors (4384805).

21791515 is a wasteful number, since it uses less digits than its factorization.

21791515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4421.

The product of its digits is 3150, while the sum is 31.

The square root of 21791515 is about 4668.1382798713. The cubic root of 21791515 is about 279.3159962443.

The spelling of 21791515 in words is "twenty-one million, seven hundred ninety-one thousand, five hundred fifteen".