21074729 has 4 divisors (see below), whose sum is σ = 22695876. Its totient is φ = 19453584.

The previous prime is 21074689. The next prime is 21074737. The reversal of 21074729 is 92747012.

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 5290000 + 15784729 = 2300^2 + 3973^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21074729 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21074695 and 21074704.

It is not an unprimeable number, because it can be changed into a prime (21074129) 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, 810554 + ... + 810579.

It is an arithmetic number, because the mean of its divisors is an integer number (5673969).

Almost surely, 2^21074729 is an apocalyptic number.

It is an amenable number.

21074729 is a deficient number, since it is larger than the sum of its proper divisors (1621147).

21074729 is a wasteful number, since it uses less digits than its factorization.

21074729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1621146.

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 21074729 is about 4590.7220564961. The cubic root of 21074729 is about 276.2192867993.

The spelling of 21074729 in words is "twenty-one million, seventy-four thousand, seven hundred twenty-nine".