21405012 has 12 divisors (see below), whose sum is σ = 49945056. Its totient is φ = 7135000.

The previous prime is 21404983. The next prime is 21405047. The reversal of 21405012 is 21050412.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 21404982 and 21405000.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 891864 + ... + 891887.

It is an arithmetic number, because the mean of its divisors is an integer number (4162088).

Almost surely, 2^21405012 is an apocalyptic number.

It is an amenable number.

21405012 is an abundant number, since it is smaller than the sum of its proper divisors (28540044).

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

21405012 is a wasteful number, since it uses less digits than its factorization.

21405012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1783758 (or 1783756 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21405012 is about 4626.5550899130. Note that the first 3 decimals coincide. The cubic root of 21405012 is about 277.6547825731.

Adding to 21405012 its reverse (21050412), we get a palindrome (42455424).

The spelling of 21405012 in words is "twenty-one million, four hundred five thousand, twelve".