21809006 has 4 divisors (see below), whose sum is σ = 32713512. Its totient is φ = 10904502.

The previous prime is 21809003. The next prime is 21809009. The reversal of 21809006 is 60090812.

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 (21809003) and next prime (21809009).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21809003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5452250 + ... + 5452253.

It is an arithmetic number, because the mean of its divisors is an integer number (8178378).

Almost surely, 2^21809006 is an apocalyptic number.

21809006 is a deficient number, since it is larger than the sum of its proper divisors (10904506).

21809006 is a wasteful number, since it uses less digits than its factorization.

21809006 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10904505.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21809006 is about 4670.0113490226. The cubic root of 21809006 is about 279.3907074266.

Adding to 21809006 its reverse (60090812), we get a palindrome (81899818).

The spelling of 21809006 in words is "twenty-one million, eight hundred nine thousand, six".