40640721 has 16 divisors (see below), whose sum is σ = 61022208. Its totient is φ = 23835600.

The previous prime is 40640707. The next prime is 40640723. The reversal of 40640721 is 12704604.

It is not a de Polignac number, because 40640721 - 2⁶ = 40640657 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 40640691 and 40640700.

It is not an unprimeable number, because it can be changed into a prime (40640723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18841 + ... + 20886.

It is an arithmetic number, because the mean of its divisors is an integer number (3813888).

Almost surely, 2^40640721 is an apocalyptic number.

It is an amenable number.

40640721 is a deficient number, since it is larger than the sum of its proper divisors (20381487).

40640721 is a wasteful number, since it uses less digits than its factorization.

40640721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39772.

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 40640721 is about 6375.0075294073. The cubic root of 40640721 is about 343.8115545527.

The spelling of 40640721 in words is "forty million, six hundred forty thousand, seven hundred twenty-one".