3949921561 has 4 divisors (see below), whose sum is σ = 3952586512. Its totient is φ = 3947256612.

The previous prime is 3949921517. The next prime is 3949921567. The reversal of 3949921561 is 1651299493.

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.

It is a cyclic number.

It is not a de Polignac number, because 3949921561 - 2¹⁹ = 3949397273 is a prime.

It is not an unprimeable number, because it can be changed into a prime (3949921567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1330251 + ... + 1333216.

It is an arithmetic number, because the mean of its divisors is an integer number (988146628).

Almost surely, 2^3949921561 is an apocalyptic number.

It is an amenable number.

3949921561 is a deficient number, since it is larger than the sum of its proper divisors (2664951).

3949921561 is a wasteful number, since it uses less digits than its factorization.

3949921561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2664950.

The product of its digits is 524880, while the sum is 49.

The square root of 3949921561 is about 62848.4014196065. The cubic root of 3949921561 is about 1580.7486652529.

The spelling of 3949921561 in words is "three billion, nine hundred forty-nine million, nine hundred twenty-one thousand, five hundred sixty-one".