21465921 has 16 divisors (see below), whose sum is σ = 29179904. Its totient is φ = 14034384.

The previous prime is 21465907. The next prime is 21465937. The reversal of 21465921 is 12956412.

It is not a de Polignac number, because 21465921 - 2¹⁷ = 21334849 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21465971) 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, 38970 + ... + 39516.

It is an arithmetic number, because the mean of its divisors is an integer number (1823744).

Almost surely, 2^21465921 is an apocalyptic number.

It is an amenable number.

21465921 is a deficient number, since it is larger than the sum of its proper divisors (7713983).

21465921 is a wasteful number, since it uses less digits than its factorization.

21465921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 780.

The product of its digits is 4320, while the sum is 30.

The square root of 21465921 is about 4633.1329572979. The cubic root of 21465921 is about 277.9178932169.

The spelling of 21465921 in words is "twenty-one million, four hundred sixty-five thousand, nine hundred twenty-one".