21005964 has 36 divisors (see below), whose sum is σ = 60684624. Its totient is φ = 6001632.

The previous prime is 21005953. The next prime is 21005977. The reversal of 21005964 is 46950012.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-3 number, since 3×21005964³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 41427 + ... + 41930.

It is an arithmetic number, because the mean of its divisors is an integer number (1685684).

Almost surely, 2^21005964 is an apocalyptic number.

It is an amenable number.

21005964 is an abundant number, since it is smaller than the sum of its proper divisors (39678660).

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

21005964 is a wasteful number, since it uses less digits than its factorization.

21005964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83374 (or 83369 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21005964 is about 4583.2263745096. The cubic root of 21005964 is about 275.9185329816.

Adding to 21005964 its reverse (46950012), we get a palindrome (67955976).

The spelling of 21005964 in words is "twenty-one million, five thousand, nine hundred sixty-four".