21578612 has 24 divisors (see below), whose sum is σ = 41332032. Its totient is φ = 9776000.

The previous prime is 21578597. The next prime is 21578617. The reversal of 21578612 is 21687512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21578617) 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 7 ways as a sum of consecutive naturals, for example, 17033 + ... + 18255.

It is an arithmetic number, because the mean of its divisors is an integer number (1722168).

Almost surely, 2^21578612 is an apocalyptic number.

21578612 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21578612 is a deficient number, since it is larger than the sum of its proper divisors (19753420).

21578612 is a wasteful number, since it uses less digits than its factorization.

21578612 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1639 (or 1637 counting only the distinct ones).

The product of its digits is 6720, while the sum is 32.

The square root of 21578612 is about 4645.2784631279. The cubic root of 21578612 is about 278.4033790106.

Subtracting 21578612 from its reverse (21687512), we obtain a square (108900 = 330²).

The spelling of 21578612 in words is "twenty-one million, five hundred seventy-eight thousand, six hundred twelve".