21721274 has 8 divisors (see below), whose sum is σ = 34498548. Its totient is φ = 10221760.

The previous prime is 21721253. The next prime is 21721277. The reversal of 21721274 is 47212712.

It can be written as a sum of positive squares in 2 ways, for example, as 19492225 + 2229049 = 4415^2 + 1493^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21721277) by changing a digit.

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, 319397 + ... + 319464.

Almost surely, 2^21721274 is an apocalyptic number.

21721274 is a deficient number, since it is larger than the sum of its proper divisors (12777274).

21721274 is a wasteful number, since it uses less digits than its factorization.

21721274 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 638880.

The product of its digits is 1568, while the sum is 26.

The square root of 21721274 is about 4660.6087585207. The cubic root of 21721274 is about 279.0155650502.

Adding to 21721274 its reverse (47212712), we get a palindrome (68933986).

It can be divided in two parts, 2172 and 1274, that multiplied together give a triangular number (2767128 = T₂₃₅₂).

The spelling of 21721274 in words is "twenty-one million, seven hundred twenty-one thousand, two hundred seventy-four".