21909143 has 4 divisors (see below), whose sum is σ = 22501320. Its totient is φ = 21316968.

The previous prime is 21909131. The next prime is 21909161. The reversal of 21909143 is 34190912.

It is a happy number.

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 21909143 - 2⁶ = 21909079 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 (21909103) 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, 296033 + ... + 296106.

It is an arithmetic number, because the mean of its divisors is an integer number (5625330).

Almost surely, 2^21909143 is an apocalyptic number.

21909143 is a deficient number, since it is larger than the sum of its proper divisors (592177).

21909143 is an equidigital number, since it uses as much as digits as its factorization.

21909143 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592176.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21909143 is about 4680.7203505443. The cubic root of 21909143 is about 279.8176661553.

The spelling of 21909143 in words is "twenty-one million, nine hundred nine thousand, one hundred forty-three".