21573247 has 4 divisors (see below), whose sum is σ = 21782800. Its totient is φ = 21363696.

The previous prime is 21573239. The next prime is 21573269. The reversal of 21573247 is 74237512.

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

It is a cyclic number.

It is not a de Polignac number, because 21573247 - 2³ = 21573239 is a prime.

It is a super-2 number, since 2×21573247² = 930809972246018, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21573547) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104622 + ... + 104827.

It is an arithmetic number, because the mean of its divisors is an integer number (5445700).

Almost surely, 2^21573247 is an apocalyptic number.

21573247 is a deficient number, since it is larger than the sum of its proper divisors (209553).

21573247 is a wasteful number, since it uses less digits than its factorization.

21573247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209552.

The product of its digits is 11760, while the sum is 31.

The square root of 21573247 is about 4644.7009591577. The cubic root of 21573247 is about 278.3803043425.

The spelling of 21573247 in words is "twenty-one million, five hundred seventy-three thousand, two hundred forty-seven".