661220351 has 6 divisors (see below), whose sum is σ = 726796056. Its totient is φ = 601109300.

The previous prime is 661220333. The next prime is 661220363. The reversal of 661220351 is 153022166.

It is a de Polignac number, because none of the positive numbers 2^k-661220351 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 661220351.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661220251) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2732195 + ... + 2732436.

It is an arithmetic number, because the mean of its divisors is an integer number (121132676).

Almost surely, 2^661220351 is an apocalyptic number.

661220351 is a deficient number, since it is larger than the sum of its proper divisors (65575705).

661220351 is a wasteful number, since it uses less digits than its factorization.

661220351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5464653 (or 5464642 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 661220351 is about 25714.2052375725. The cubic root of 661220351 is about 871.1950595747.

The spelling of 661220351 in words is "six hundred sixty-one million, two hundred twenty thousand, three hundred fifty-one".