21017963 has 4 divisors (see below), whose sum is σ = 21030360. Its totient is φ = 21005568.

The previous prime is 21017951. The next prime is 21017981. The reversal of 21017963 is 36971012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21017963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21017993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3158 + ... + 7211.

It is an arithmetic number, because the mean of its divisors is an integer number (5257590).

Almost surely, 2^21017963 is an apocalyptic number.

21017963 is a deficient number, since it is larger than the sum of its proper divisors (12397).

21017963 is a wasteful number, since it uses less digits than its factorization.

21017963 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12396.

The product of its (nonzero) digits is 2268, while the sum is 29.

The square root of 21017963 is about 4584.5351999957. The cubic root of 21017963 is about 275.9710595924.

Adding to 21017963 its reverse (36971012), we get a palindrome (57988975).

The spelling of 21017963 in words is "twenty-one million, seventeen thousand, nine hundred sixty-three".