40240721 has 4 divisors (see below), whose sum is σ = 41222244. Its totient is φ = 39259200.

The previous prime is 40240709. The next prime is 40240787. The reversal of 40240721 is 12704204.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19891600 + 20349121 = 4460^2 + 4511^2 .

It is a cyclic number.

It is not a de Polignac number, because 40240721 - 2⁶ = 40240657 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 40240693 and 40240702.

It is not an unprimeable number, because it can be changed into a prime (40242721) 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, 490700 + ... + 490781.

It is an arithmetic number, because the mean of its divisors is an integer number (10305561).

Almost surely, 2^40240721 is an apocalyptic number.

40240721 is a gapful number since it is divisible by the number (41) formed by its first and last digit.

It is an amenable number.

40240721 is a deficient number, since it is larger than the sum of its proper divisors (981523).

40240721 is an equidigital number, since it uses as much as digits as its factorization.

40240721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 981522.

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 40240721 is about 6343.5574404273. The cubic root of 40240721 is about 342.6798629055.

Adding to 40240721 its reverse (12704204), we get a palindrome (52944925).

The spelling of 40240721 in words is "forty million, two hundred forty thousand, seven hundred twenty-one".