21729634 has 4 divisors (see below), whose sum is σ = 32594454. Its totient is φ = 10864816.

The previous prime is 21729611. The next prime is 21729637. The reversal of 21729634 is 43692712.

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

It can be written as a sum of positive squares in only one way, i.e., 12938409 + 8791225 = 3597^2 + 2965^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21729634.

It is not an unprimeable number, because it can be changed into a prime (21729637) 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 as a sum of consecutive naturals, namely, 5432407 + ... + 5432410.

Almost surely, 2^21729634 is an apocalyptic number.

21729634 is a deficient number, since it is larger than the sum of its proper divisors (10864820).

21729634 is a wasteful number, since it uses less digits than its factorization.

21729634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10864819.

The product of its digits is 18144, while the sum is 34.

The square root of 21729634 is about 4661.5055507851. The cubic root of 21729634 is about 279.0513559364.

The spelling of 21729634 in words is "twenty-one million, seven hundred twenty-nine thousand, six hundred thirty-four".