21249679 has 4 divisors (see below), whose sum is σ = 23181480. Its totient is φ = 19317880.

The previous prime is 21249673. The next prime is 21249691. The reversal of 21249679 is 97694212.

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 21249679 - 2³ = 21249671 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21249671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 965884 + ... + 965905.

It is an arithmetic number, because the mean of its divisors is an integer number (5795370).

Almost surely, 2^21249679 is an apocalyptic number.

21249679 is a deficient number, since it is larger than the sum of its proper divisors (1931801).

21249679 is a wasteful number, since it uses less digits than its factorization.

21249679 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1931800.

The product of its digits is 54432, while the sum is 40.

The square root of 21249679 is about 4609.7374111765. The cubic root of 21249679 is about 276.9815181403.

The spelling of 21249679 in words is "twenty-one million, two hundred forty-nine thousand, six hundred seventy-nine".