21491275 has 24 divisors (see below), whose sum is σ = 29060640. Its totient is φ = 15671040.

The previous prime is 21491263. The next prime is 21491287. The reversal of 21491275 is 57219412.

It is an interprime number because it is at equal distance from previous prime (21491263) and next prime (21491287).

It is a de Polignac number, because none of the positive numbers 2^k-21491275 is a prime.

It is a super-2 number, since 2×21491275² = 923749802251250, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 28554 + ... + 29296.

It is an arithmetic number, because the mean of its divisors is an integer number (1210860).

Almost surely, 2^21491275 is an apocalyptic number.

21491275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21491275 is a deficient number, since it is larger than the sum of its proper divisors (7569365).

21491275 is a wasteful number, since it uses less digits than its factorization.

21491275 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 855 (or 850 counting only the distinct ones).

The product of its digits is 5040, while the sum is 31.

The square root of 21491275 is about 4635.8683113307. The cubic root of 21491275 is about 278.0272690329.

The spelling of 21491275 in words is "twenty-one million, four hundred ninety-one thousand, two hundred seventy-five".