21213963 has 12 divisors (see below), whose sum is σ = 30754360. Its totient is φ = 14090976.

The previous prime is 21213947. The next prime is 21213971. The reversal of 21213963 is 36931212.

It is not a de Polignac number, because 21213963 - 2⁴ = 21213947 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21213923) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1618 + ... + 6711.

Almost surely, 2^21213963 is an apocalyptic number.

21213963 is a deficient number, since it is larger than the sum of its proper divisors (9540397).

21213963 is a wasteful number, since it uses less digits than its factorization.

21213963 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8618 (or 8615 counting only the distinct ones).

The product of its digits is 1944, while the sum is 27.

The square root of 21213963 is about 4605.8618086087. The cubic root of 21213963 is about 276.8262496058.

It can be divided in two parts, 2121 and 3963, that added together give a square (6084 = 78²).

The spelling of 21213963 in words is "twenty-one million, two hundred thirteen thousand, nine hundred sixty-three".