21731145 has 8 divisors (see below), whose sum is σ = 34769856. Its totient is φ = 11589936.

The previous prime is 21731141. The next prime is 21731147. The reversal of 21731145 is 54113712.

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

It is not a de Polignac number, because 21731145 - 2² = 21731141 is a prime.

It is a super-2 number, since 2×21731145² = 944485326022050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21731141) 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 7 ways as a sum of consecutive naturals, for example, 724357 + ... + 724386.

It is an arithmetic number, because the mean of its divisors is an integer number (4346232).

Almost surely, 2^21731145 is an apocalyptic number.

It is an amenable number.

21731145 is a deficient number, since it is larger than the sum of its proper divisors (13038711).

21731145 is a wasteful number, since it uses less digits than its factorization.

21731145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1448751.

The product of its digits is 840, while the sum is 24.

The square root of 21731145 is about 4661.6676200690. The cubic root of 21731145 is about 279.0578238598.

Adding to 21731145 its reverse (54113712), we get a palindrome (75844857).

The spelling of 21731145 in words is "twenty-one million, seven hundred thirty-one thousand, one hundred forty-five".