21145147 has 4 divisors (see below), whose sum is σ = 21874320. Its totient is φ = 20415976.

The previous prime is 21145141. The next prime is 21145169. The reversal of 21145147 is 74154112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21145147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21145141) 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, 364543 + ... + 364600.

It is an arithmetic number, because the mean of its divisors is an integer number (5468580).

Almost surely, 2^21145147 is an apocalyptic number.

21145147 is a deficient number, since it is larger than the sum of its proper divisors (729173).

21145147 is an equidigital number, since it uses as much as digits as its factorization.

21145147 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 729172.

The product of its digits is 1120, while the sum is 25.

The square root of 21145147 is about 4598.3852600668. The cubic root of 21145147 is about 276.5265930188.

Adding to 21145147 its reverse (74154112), we get a palindrome (95299259).

The spelling of 21145147 in words is "twenty-one million, one hundred forty-five thousand, one hundred forty-seven".