21012145 has 16 divisors (see below), whose sum is σ = 31436928. Its totient is φ = 13098240.

The previous prime is 21012137. The next prime is 21012151. The reversal of 21012145 is 54121012.

It is not a de Polignac number, because 21012145 - 2³ = 21012137 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is an unprimeable number.

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, 26904 + ... + 27673.

It is an arithmetic number, because the mean of its divisors is an integer number (1964808).

Almost surely, 2^21012145 is an apocalyptic number.

It is an amenable number.

21012145 is a deficient number, since it is larger than the sum of its proper divisors (10424783).

21012145 is a wasteful number, since it uses less digits than its factorization.

21012145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54600.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21012145 is about 4583.9006315582. The cubic root of 21012145 is about 275.9455933155.

Adding to 21012145 its reverse (54121012), we get a palindrome (75133157).

The spelling of 21012145 in words is "twenty-one million, twelve thousand, one hundred forty-five".