21057011 has 4 divisors (see below), whose sum is σ = 21261552. Its totient is φ = 20852472.

The previous prime is 21057007. The next prime is 21057013. The reversal of 21057011 is 11075012.

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

It is a cyclic number.

It is not a de Polignac number, because 21057011 - 2² = 21057007 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21057013) 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 in 3 ways as a sum of consecutive naturals, for example, 102116 + ... + 102321.

It is an arithmetic number, because the mean of its divisors is an integer number (5315388).

Almost surely, 2^21057011 is an apocalyptic number.

21057011 is a deficient number, since it is larger than the sum of its proper divisors (204541).

21057011 is a wasteful number, since it uses less digits than its factorization.

21057011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204540.

The product of its (nonzero) digits is 70, while the sum is 17.

The square root of 21057011 is about 4588.7918889398. The cubic root of 21057011 is about 276.1418571682.

The spelling of 21057011 in words is "twenty-one million, fifty-seven thousand, eleven".