21123071 has 4 divisors (see below), whose sum is σ = 21277392. Its totient is φ = 20968752.

The previous prime is 21123043. The next prime is 21123073. The reversal of 21123071 is 17032112.

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 21123071 - 2²² = 16928767 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123073) 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, 76955 + ... + 77228.

It is an arithmetic number, because the mean of its divisors is an integer number (5319348).

Almost surely, 2^21123071 is an apocalyptic number.

21123071 is a deficient number, since it is larger than the sum of its proper divisors (154321).

21123071 is a wasteful number, since it uses less digits than its factorization.

21123071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154320.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21123071 is about 4595.9842253863. The cubic root of 21123071 is about 276.4303262214.

Adding to 21123071 its reverse (17032112), we get a palindrome (38155183).

The spelling of 21123071 in words is "twenty-one million, one hundred twenty-three thousand, seventy-one".