21729170 has 8 divisors (see below), whose sum is σ = 39112524. Its totient is φ = 8691664.

The previous prime is 21729161. The next prime is 21729199. The reversal of 21729170 is 7192712.

It can be written as a sum of positive squares in 2 ways, for example, as 21520321 + 208849 = 4639^2 + 457^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1086449 + ... + 1086468.

Almost surely, 2^21729170 is an apocalyptic number.

21729170 is a deficient number, since it is larger than the sum of its proper divisors (17383354).

21729170 is a wasteful number, since it uses less digits than its factorization.

21729170 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2172924.

The product of its (nonzero) digits is 1764, while the sum is 29.

The square root of 21729170 is about 4661.4557811911. The cubic root of 21729170 is about 279.0493696972.

It can be divided in two parts, 217291 and 70, that multiplied together give a triangular number (15210370 = T₅₅₁₅).

The spelling of 21729170 in words is "twenty-one million, seven hundred twenty-nine thousand, one hundred seventy".