21491147 has 4 divisors (see below), whose sum is σ = 22622280. Its totient is φ = 20360016.

The previous prime is 21491101. The next prime is 21491149. The reversal of 21491147 is 74119412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21491147 - 2¹² = 21487051 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21491149) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 565538 + ... + 565575.

It is an arithmetic number, because the mean of its divisors is an integer number (5655570).

Almost surely, 2^21491147 is an apocalyptic number.

21491147 is a deficient number, since it is larger than the sum of its proper divisors (1131133).

21491147 is a wasteful number, since it uses less digits than its factorization.

21491147 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1131132.

The product of its digits is 2016, while the sum is 29.

The square root of 21491147 is about 4635.8545059137. The cubic root of 21491147 is about 278.0267170638.

The spelling of 21491147 in words is "twenty-one million, four hundred ninety-one thousand, one hundred forty-seven".