21719247 has 8 divisors (see below), whose sum is σ = 31591680. Its totient is φ = 13163160.

The previous prime is 21719239. The next prime is 21719263. The reversal of 21719247 is 74291712.

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

It is not a de Polignac number, because 21719247 - 2³ = 21719239 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33), and also a Moran number because the ratio is a prime number: 658159 = 21719247 / (2 + 1 + 7 + 1 + 9 + 2 + 4 + 7).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21719207) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 329047 + ... + 329112.

It is an arithmetic number, because the mean of its divisors is an integer number (3948960).

Almost surely, 2^21719247 is an apocalyptic number.

21719247 is a deficient number, since it is larger than the sum of its proper divisors (9872433).

21719247 is a wasteful number, since it uses less digits than its factorization.

21719247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 658173.

The product of its digits is 7056, while the sum is 33.

The square root of 21719247 is about 4660.3912925848. The cubic root of 21719247 is about 279.0068856614.

The spelling of 21719247 in words is "twenty-one million, seven hundred nineteen thousand, two hundred forty-seven".