21729933 has 18 divisors (see below), whose sum is σ = 32099054. Its totient is φ = 14165424.

The previous prime is 21729931. The next prime is 21729937. The reversal of 21729933 is 33992712.

It can be written as a sum of positive squares in only one way, i.e., 21650409 + 79524 = 4653^2 + 282^2 .

It is not a de Polignac number, because 21729933 - 2¹ = 21729931 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 (21729931) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 19335 + ... + 20427.

Almost surely, 2^21729933 is an apocalyptic number.

It is an amenable number.

21729933 is a deficient number, since it is larger than the sum of its proper divisors (10369121).

21729933 is a wasteful number, since it uses less digits than its factorization.

21729933 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1193 (or 1143 counting only the distinct ones).

The product of its digits is 20412, while the sum is 36.

The square root of 21729933 is about 4661.5376218583. The cubic root of 21729933 is about 279.0526358471.

The spelling of 21729933 in words is "twenty-one million, seven hundred twenty-nine thousand, nine hundred thirty-three".