21090606 has 8 divisors (see below), whose sum is σ = 42181224. Its totient is φ = 7030200.

The previous prime is 21090583. The next prime is 21090631. The reversal of 21090606 is 60609012.

It is a sphenic number, since it is the product of 3 distinct primes.

21090606 is an admirable number.

It is a super-2 number, since 2×21090606² = 889627322894472, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1757545 + ... + 1757556.

It is an arithmetic number, because the mean of its divisors is an integer number (5272653).

Almost surely, 2^21090606 is an apocalyptic number.

21090606 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21090606 is a wasteful number, since it uses less digits than its factorization.

21090606 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3515106.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21090606 is about 4592.4509795968. The cubic root of 21090606 is about 276.2886341959.

Adding to 21090606 its reverse (60609012), we get a palindrome (81699618).

The spelling of 21090606 in words is "twenty-one million, ninety thousand, six hundred six".