21909007 has 4 divisors (see below), whose sum is σ = 22664520. Its totient is φ = 21153496.

The previous prime is 21908989. The next prime is 21909029. The reversal of 21909007 is 70090912.

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 21909007 - 2¹⁹ = 21384719 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 (21909077) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 377713 + ... + 377770.

It is an arithmetic number, because the mean of its divisors is an integer number (5666130).

Almost surely, 2^21909007 is an apocalyptic number.

21909007 is a deficient number, since it is larger than the sum of its proper divisors (755513).

21909007 is an equidigital number, since it uses as much as digits as its factorization.

21909007 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 755512.

The product of its (nonzero) digits is 1134, while the sum is 28.

The square root of 21909007 is about 4680.7058228434. The cubic root of 21909007 is about 279.8170871690.

Adding to 21909007 its reverse (70090912), we get a palindrome (91999919).

The spelling of 21909007 in words is "twenty-one million, nine hundred nine thousand, seven".