21057611 has 4 divisors (see below), whose sum is σ = 22296312. Its totient is φ = 19818912.

The previous prime is 21057599. The next prime is 21057623. The reversal of 21057611 is 11675012.

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

It is an interprime number because it is at equal distance from previous prime (21057599) and next prime (21057623).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21057611 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21057661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 619325 + ... + 619358.

It is an arithmetic number, because the mean of its divisors is an integer number (5574078).

Almost surely, 2^21057611 is an apocalyptic number.

21057611 is a deficient number, since it is larger than the sum of its proper divisors (1238701).

21057611 is a wasteful number, since it uses less digits than its factorization.

21057611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1238700.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21057611 is about 4588.8572651587. The cubic root of 21057611 is about 276.1444799453.

The spelling of 21057611 in words is "twenty-one million, fifty-seven thousand, six hundred eleven".