2639721 has 16 divisors (see below), whose sum is σ = 4045184. Its totient is φ = 1499904.

The previous prime is 2639711. The next prime is 2639723. The reversal of 2639721 is 1279362.

It is not a de Polignac number, because 2639721 - 2¹⁰ = 2638697 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2639723) 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, 6891 + ... + 7263.

It is an arithmetic number, because the mean of its divisors is an integer number (252824).

2^2639721 is an apocalyptic number.

2639721 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2639721 is a deficient number, since it is larger than the sum of its proper divisors (1405463).

2639721 is a wasteful number, since it uses less digits than its factorization.

2639721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 720.

The product of its digits is 4536, while the sum is 30.

The square root of 2639721 is about 1624.7218223438. The cubic root of 2639721 is about 138.2035957214.

The spelling of 2639721 in words is "two million, six hundred thirty-nine thousand, seven hundred twenty-one".