3765780721 has 4 divisors (see below), whose sum is σ = 3987297252. Its totient is φ = 3544264192.

The previous prime is 3765780643. The next prime is 3765780737. The reversal of 3765780721 is 1270875673.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1270875673 = 11551 ⋅110023.

It can be written as a sum of positive squares in 2 ways, for example, as 2891750625 + 874030096 = 53775^2 + 29564^2 .

It is a cyclic number.

It is not a de Polignac number, because 3765780721 - 2²¹ = 3763683569 is a prime.

It is a super-2 number, since 2×3765780721² = 28362208877310559682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3765780121) 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, 110758240 + ... + 110758273.

It is an arithmetic number, because the mean of its divisors is an integer number (996824313).

Almost surely, 2^3765780721 is an apocalyptic number.

It is an amenable number.

3765780721 is a deficient number, since it is larger than the sum of its proper divisors (221516531).

3765780721 is a wasteful number, since it uses less digits than its factorization.

3765780721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221516530.

The product of its (nonzero) digits is 493920, while the sum is 46.

The square root of 3765780721 is about 61365.9573460726. The cubic root of 3765780721 is about 1555.7925084256.

The spelling of 3765780721 in words is "three billion, seven hundred sixty-five million, seven hundred eighty thousand, seven hundred twenty-one".