6920409721 has 9 divisors (see below), whose sum is σ = 7096814733. Its totient is φ = 6748291680.

The previous prime is 6920409707. The next prime is 6920409733. The reversal of 6920409721 is 1279040296.

The square root of 6920409721 is 83189.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 120758121 + 6799651600 = 10989^2 + 82460^2 .

It is not a de Polignac number, because 6920409721 - 2¹⁹ = 6919885433 is a prime.

It is a super-2 number, since 2×6920409721² = 95784141413022595682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6920409701) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3409735 + ... + 3411763.

Almost surely, 2^6920409721 is an apocalyptic number.

6920409721 is the 83189-th square number.

6920409721 is the 41595-th centered octagonal number.

It is an amenable number.

6920409721 is a deficient number, since it is larger than the sum of its proper divisors (176405012).

6920409721 is an frugal number, since it uses more digits than its factorization.

6920409721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4140 (or 2070 counting only the distinct ones).

The product of its (nonzero) digits is 54432, while the sum is 40.

The cubic root of 6920409721 is about 1905.6534955526.

The spelling of 6920409721 in words is "six billion, nine hundred twenty million, four hundred nine thousand, seven hundred twenty-one".