21874729 has 4 divisors (see below), whose sum is σ = 22629060. Its totient is φ = 21120400.

The previous prime is 21874711. The next prime is 21874751. The reversal of 21874729 is 92747812.

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 11377129 + 10497600 = 3373^2 + 3240^2 .

It is a cyclic number.

It is not a de Polignac number, because 21874729 - 2²¹ = 19777577 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 = 21874691 and 21874700.

It is not an unprimeable number, because it can be changed into a prime (21874709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 377122 + ... + 377179.

It is an arithmetic number, because the mean of its divisors is an integer number (5657265).

Almost surely, 2^21874729 is an apocalyptic number.

21874729 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21874729 is a deficient number, since it is larger than the sum of its proper divisors (754331).

21874729 is an equidigital number, since it uses as much as digits as its factorization.

21874729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 754330.

The product of its digits is 56448, while the sum is 40.

The square root of 21874729 is about 4677.0427622591. The cubic root of 21874729 is about 279.6710806024.

It can be divided in two parts, 218 and 74729, that added together give a palindrome (74947).

The spelling of 21874729 in words is "twenty-one million, eight hundred seventy-four thousand, seven hundred twenty-nine".