2720921 has 6 divisors (see below), whose sum is σ = 3165210. Its totient is φ = 2332176.

The previous prime is 2720917. The next prime is 2720953. The reversal of 2720921 is 1290272.

It can be written as a sum of positive squares in only one way, i.e., 1466521 + 1254400 = 1211^2 + 1120^2 .

It is not a de Polignac number, because 2720921 - 2² = 2720917 is a prime.

It is a super-2 number, since 2×2720921² = 14806822176482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2720981) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 27716 + ... + 27813.

It is an arithmetic number, because the mean of its divisors is an integer number (527535).

2^2720921 is an apocalyptic number.

It is an amenable number.

2720921 is a deficient number, since it is larger than the sum of its proper divisors (444289).

2720921 is an equidigital number, since it uses as much as digits as its factorization.

2720921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55543 (or 55536 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 2720921 is about 1649.5214457533. The cubic root of 2720921 is about 139.6063944274.

The spelling of 2720921 in words is "two million, seven hundred twenty thousand, nine hundred twenty-one".