21002906 has 8 divisors (see below), whose sum is σ = 32272884. Its totient is φ = 10245280.

The previous prime is 21002899. The next prime is 21002911. The reversal of 21002906 is 60920012.

It can be written as a sum of positive squares in 2 ways, for example, as 17297281 + 3705625 = 4159^2 + 1925^2 .

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

It is a super-2 number, since 2×21002906² = 882244120889672, which contains 22 as substring.

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, 127985 + ... + 128148.

Almost surely, 2^21002906 is an apocalyptic number.

21002906 is a deficient number, since it is larger than the sum of its proper divisors (11269978).

21002906 is a wasteful number, since it uses less digits than its factorization.

21002906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256176.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21002906 is about 4582.8927545820. The cubic root of 21002906 is about 275.9051431363.

Adding to 21002906 its reverse (60920012), we get a palindrome (81922918).

The spelling of 21002906 in words is "twenty-one million, two thousand, nine hundred six".