21123571 has 16 divisors (see below), whose sum is σ = 26447040. Its totient is φ = 16450560.

The previous prime is 21123533. The next prime is 21123589. The reversal of 21123571 is 17532112.

It is a happy number.

It is not a de Polignac number, because 21123571 - 2¹³ = 21115379 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 391 + ... + 6511.

It is an arithmetic number, because the mean of its divisors is an integer number (1652940).

Almost surely, 2^21123571 is an apocalyptic number.

21123571 is a deficient number, since it is larger than the sum of its proper divisors (5323469).

21123571 is a wasteful number, since it uses less digits than its factorization.

21123571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6174.

The product of its digits is 420, while the sum is 22.

The square root of 21123571 is about 4596.0386203773. The cubic root of 21123571 is about 276.4325073132.

Adding to 21123571 its reverse (17532112), we get a palindrome (38655683).

The spelling of 21123571 in words is "twenty-one million, one hundred twenty-three thousand, five hundred seventy-one".