21491547 has 24 divisors (see below), whose sum is σ = 36366912. Its totient is φ = 11163600.

The previous prime is 21491539. The next prime is 21491563. The reversal of 21491547 is 74519412.

It is a happy number.

It is not a de Polignac number, because 21491547 - 2³ = 21491539 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21491537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5029 + ... + 8262.

It is an arithmetic number, because the mean of its divisors is an integer number (1515288).

Almost surely, 2^21491547 is an apocalyptic number.

21491547 is a deficient number, since it is larger than the sum of its proper divisors (14875365).

21491547 is a wasteful number, since it uses less digits than its factorization.

21491547 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13319 (or 13312 counting only the distinct ones).

The product of its digits is 10080, while the sum is 33.

The square root of 21491547 is about 4635.8976477054. The cubic root of 21491547 is about 278.0284419600.

The spelling of 21491547 in words is "twenty-one million, four hundred ninety-one thousand, five hundred forty-seven".