21144547 has 2 divisors, whose sum is σ = 21144548. Its totient is φ = 21144546.

The previous prime is 21144469. The next prime is 21144551. The reversal of 21144547 is 74544112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21144547 - 2⁷ = 21144419 is a prime.

It is equal to p_1338535 and since 21144547 and 1338535 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21144577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572273 + 10572274.

It is an arithmetic number, because the mean of its divisors is an integer number (10572274).

Almost surely, 2^21144547 is an apocalyptic number.

21144547 is a deficient number, since it is larger than the sum of its proper divisors (1).

21144547 is an equidigital number, since it uses as much as digits as its factorization.

21144547 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4480, while the sum is 28.

The square root of 21144547 is about 4598.3200193114. The cubic root of 21144547 is about 276.5239774853.

Adding to 21144547 its reverse (74544112), we get a palindrome (95688659).

The spelling of 21144547 in words is "twenty-one million, one hundred forty-four thousand, five hundred forty-seven".