3661440821 has 4 divisors (see below), whose sum is σ = 3723499200. Its totient is φ = 3599382444.

The previous prime is 3661440781. The next prime is 3661440829. The reversal of 3661440821 is 1280441663.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1280441663 = 6037 ⋅212099.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3661440821 is a prime.

It is a super-2 number, since 2×3661440821² = 26812297771370308082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3661440829) 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, 31029101 + ... + 31029218.

It is an arithmetic number, because the mean of its divisors is an integer number (930874800).

Almost surely, 2^3661440821 is an apocalyptic number.

It is an amenable number.

3661440821 is a deficient number, since it is larger than the sum of its proper divisors (62058379).

3661440821 is an equidigital number, since it uses as much as digits as its factorization.

3661440821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62058378.

The product of its (nonzero) digits is 27648, while the sum is 35.

The square root of 3661440821 is about 60509.8406955431. The cubic root of 3661440821 is about 1541.2887425786.

The spelling of 3661440821 in words is "three billion, six hundred sixty-one million, four hundred forty thousand, eight hundred twenty-one".