21651043 has 2 divisors, whose sum is σ = 21651044. Its totient is φ = 21651042.

The previous prime is 21651017. The next prime is 21651101. The reversal of 21651043 is 34015612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21651043 - 2⁵ = 21651011 is a prime.

It is not a weakly prime, because it can be changed into another prime (21651943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825521 + 10825522.

It is an arithmetic number, because the mean of its divisors is an integer number (10825522).

Almost surely, 2^21651043 is an apocalyptic number.

21651043 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651043 is an equidigital number, since it uses as much as digits as its factorization.

21651043 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21651043 is about 4653.0681275907. The cubic root of 21651043 is about 278.7145283880.

Adding to 21651043 its reverse (34015612), we get a palindrome (55666655).

The spelling of 21651043 in words is "twenty-one million, six hundred fifty-one thousand, forty-three".