105209721 has 24 divisors (see below), whose sum is σ = 155151360. Its totient is φ = 68687136.

The previous prime is 105209701. The next prime is 105209723. The reversal of 105209721 is 127902501.

It is not a de Polignac number, because 105209721 - 2¹³ = 105201529 is a prime.

It is a super-2 number, since 2×105209721² = 22138170785795682, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (105209723) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 94315 + ... + 95423.

It is an arithmetic number, because the mean of its divisors is an integer number (6464640).

Almost surely, 2^105209721 is an apocalyptic number.

It is an amenable number.

105209721 is a deficient number, since it is larger than the sum of its proper divisors (49941639).

105209721 is a wasteful number, since it uses less digits than its factorization.

105209721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1325 (or 1322 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 105209721 is about 10257.1789981456. The cubic root of 105209721 is about 472.0832842240.

The spelling of 105209721 in words is "one hundred five million, two hundred nine thousand, seven hundred twenty-one".