21019679 has 4 divisors (see below), whose sum is σ = 21042384. Its totient is φ = 20996976.

The previous prime is 21019657. The next prime is 21019699. The reversal of 21019679 is 97691012.

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-21019679 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019699) 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, 9902 + ... + 11835.

It is an arithmetic number, because the mean of its divisors is an integer number (5260596).

Almost surely, 2^21019679 is an apocalyptic number.

21019679 is a deficient number, since it is larger than the sum of its proper divisors (22705).

21019679 is an equidigital number, since it uses as much as digits as its factorization.

21019679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22704.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 21019679 is about 4584.7223471002. The cubic root of 21019679 is about 275.9785698897.

The spelling of 21019679 in words is "twenty-one million, nineteen thousand, six hundred seventy-nine".