21421584 has 50 divisors (see below), whose sum is σ = 62004030. Its totient is φ = 7140096.

The previous prime is 21421559. The next prime is 21421597. The reversal of 21421584 is 48512412.

It can be written as a sum of positive squares in only one way, i.e., 20903184 + 518400 = 4572^2 + 720^2 .

It is a super-2 number, since 2×21421584² = 917768522138112, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

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 9 ways as a sum of consecutive naturals, for example, 6969 + ... + 9560.

Almost surely, 2^21421584 is an apocalyptic number.

21421584 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21421584 is an abundant number, since it is smaller than the sum of its proper divisors (40582446).

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

21421584 is a wasteful number, since it uses less digits than its factorization.

21421584 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16549 (or 16534 counting only the distinct ones).

The product of its digits is 2560, while the sum is 27.

The square root of 21421584 is about 4628.3457087819. The cubic root of 21421584 is about 277.7264185698.

Adding to 21421584 its reverse (48512412), we get a palindrome (69933996).

The spelling of 21421584 in words is "twenty-one million, four hundred twenty-one thousand, five hundred eighty-four".