21249689 has 4 divisors (see below), whose sum is σ = 21264420. Its totient is φ = 21234960.

The previous prime is 21249673. The next prime is 21249691. The reversal of 21249689 is 98694212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12369289 + 8880400 = 3517^2 + 2980^2 .

It is a cyclic number.

It is not a de Polignac number, because 21249689 - 2⁴ = 21249673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21249589) 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, 4934 + ... + 8175.

It is an arithmetic number, because the mean of its divisors is an integer number (5316105).

Almost surely, 2^21249689 is an apocalyptic number.

It is an amenable number.

21249689 is a deficient number, since it is larger than the sum of its proper divisors (14731).

21249689 is a wasteful number, since it uses less digits than its factorization.

21249689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14730.

The product of its digits is 62208, while the sum is 41.

The square root of 21249689 is about 4609.7384958368. The cubic root of 21249689 is about 276.9815615890.

The spelling of 21249689 in words is "twenty-one million, two hundred forty-nine thousand, six hundred eighty-nine".