21809070 has 48 divisors (see below), whose sum is σ = 57519072. Its totient is φ = 5732160.

The previous prime is 21809069. The next prime is 21809071. The reversal of 21809070 is 7090812.

It is an interprime number because it is at equal distance from previous prime (21809069) and next prime (21809071).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21809071) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4684 + ... + 8096.

It is an arithmetic number, because the mean of its divisors is an integer number (1198314).

Almost surely, 2^21809070 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21809070, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28759536).

21809070 is an abundant number, since it is smaller than the sum of its proper divisors (35710002).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21809070 is a wasteful number, since it uses less digits than its factorization.

21809070 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3497 (or 3494 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 21809070 is about 4670.0182012493. The cubic root of 21809070 is about 279.3909807233.

Adding to 21809070 its reverse (7090812), we get a palindrome (28899882).

The spelling of 21809070 in words is "twenty-one million, eight hundred nine thousand, seventy".