21012043 has 16 divisors (see below), whose sum is σ = 24092320. Its totient is φ = 18164736.

The previous prime is 21011981. The next prime is 21012053. The reversal of 21012043 is 34021012.

It is a cyclic number.

It is not a de Polignac number, because 21012043 - 2⁹ = 21011531 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21012053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23521 + ... + 24397.

It is an arithmetic number, because the mean of its divisors is an integer number (1505770).

Almost surely, 2^21012043 is an apocalyptic number.

21012043 is a deficient number, since it is larger than the sum of its proper divisors (3080277).

21012043 is a wasteful number, since it uses less digits than its factorization.

21012043 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1006.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21012043 is about 4583.8895056491. The cubic root of 21012043 is about 275.9451468040.

Adding to 21012043 its reverse (34021012), we get a palindrome (55033055).

The spelling of 21012043 in words is "twenty-one million, twelve thousand, forty-three".