21508669 has 16 divisors (see below), whose sum is σ = 26853120. Its totient is φ = 16773120.

The previous prime is 21508667. The next prime is 21508673. The reversal of 21508669 is 96680512.

It is not a de Polignac number, because 21508669 - 2¹ = 21508667 is a prime.

It is a super-2 number, since 2×21508669² = 925245684303122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21508667) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 4797 + ... + 8125.

It is an arithmetic number, because the mean of its divisors is an integer number (1678320).

Almost surely, 2^21508669 is an apocalyptic number.

It is an amenable number.

21508669 is a deficient number, since it is larger than the sum of its proper divisors (5344451).

21508669 is a wasteful number, since it uses less digits than its factorization.

21508669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3420.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 21508669 is about 4637.7439558475. The cubic root of 21508669 is about 278.1022560874.

The spelling of 21508669 in words is "twenty-one million, five hundred eight thousand, six hundred sixty-nine".