661964405 has 4 divisors (see below), whose sum is σ = 794357292. Its totient is φ = 529571520.

The previous prime is 661964371. The next prime is 661964419. The reversal of 661964405 is 504469166.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 320195236 + 341769169 = 17894^2 + 18487^2 .

It is not a de Polignac number, because 661964405 - 2⁶ = 661964341 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 66196436 + ... + 66196445.

It is an arithmetic number, because the mean of its divisors is an integer number (198589323).

Almost surely, 2^661964405 is an apocalyptic number.

It is an amenable number.

661964405 is a deficient number, since it is larger than the sum of its proper divisors (132392887).

661964405 is a wasteful number, since it uses less digits than its factorization.

661964405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132392886.

The product of its (nonzero) digits is 155520, while the sum is 41.

The square root of 661964405 is about 25728.6689317578. The cubic root of 661964405 is about 871.5217147659.

The spelling of 661964405 in words is "six hundred sixty-one million, nine hundred sixty-four thousand, four hundred five".