21537143 has 4 divisors (see below), whose sum is σ = 21558360. Its totient is φ = 21515928.

The previous prime is 21537137. The next prime is 21537151. The reversal of 21537143 is 34173512.

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 21537143 - 2¹² = 21533047 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 (21537163) 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, 9005 + ... + 11142.

It is an arithmetic number, because the mean of its divisors is an integer number (5389590).

Almost surely, 2^21537143 is an apocalyptic number.

21537143 is a deficient number, since it is larger than the sum of its proper divisors (21217).

21537143 is a wasteful number, since it uses less digits than its factorization.

21537143 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21216.

The product of its digits is 2520, while the sum is 26.

The square root of 21537143 is about 4640.8127520942. The cubic root of 21537143 is about 278.2249227798.

The spelling of 21537143 in words is "twenty-one million, five hundred thirty-seven thousand, one hundred forty-three".