21249563 has 4 divisors (see below), whose sum is σ = 21310800. Its totient is φ = 21188328.

The previous prime is 21249559. The next prime is 21249583. The reversal of 21249563 is 36594212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21249563 - 2² = 21249559 is a prime.

It is a super-3 number, since 3×21249563³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21249523) 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, 30095 + ... + 30792.

It is an arithmetic number, because the mean of its divisors is an integer number (5327700).

Almost surely, 2^21249563 is an apocalyptic number.

21249563 is a deficient number, since it is larger than the sum of its proper divisors (61237).

21249563 is an equidigital number, since it uses as much as digits as its factorization.

21249563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61236.

The product of its digits is 12960, while the sum is 32.

The square root of 21249563 is about 4609.7248290977. The cubic root of 21249563 is about 276.9810141340.

It can be divided in two parts, 21249 and 563, that added together give a palindrome (21812).

The spelling of 21249563 in words is "twenty-one million, two hundred forty-nine thousand, five hundred sixty-three".