661377653 has 4 divisors (see below), whose sum is σ = 682712448. Its totient is φ = 640042860.

The previous prime is 661377643. The next prime is 661377679. The reversal of 661377653 is 356773166.

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 661377653 - 2⁶ = 661377589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661377643) 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, 10667351 + ... + 10667412.

It is an arithmetic number, because the mean of its divisors is an integer number (170678112).

Almost surely, 2^661377653 is an apocalyptic number.

It is an amenable number.

661377653 is a deficient number, since it is larger than the sum of its proper divisors (21334795).

661377653 is a wasteful number, since it uses less digits than its factorization.

661377653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21334794.

The product of its digits is 476280, while the sum is 44.

The square root of 661377653 is about 25717.2637152556. The cubic root of 661377653 is about 871.2641388458.

The spelling of 661377653 in words is "six hundred sixty-one million, three hundred seventy-seven thousand, six hundred fifty-three".