661221077 has 12 divisors (see below), whose sum is σ = 735564480. Its totient is φ = 593858760.

The previous prime is 661221053. The next prime is 661221131. The reversal of 661221077 is 770122166.

It is not a de Polignac number, because 661221077 - 2¹² = 661216981 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 (661221017) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22877 + ... + 42962.

It is an arithmetic number, because the mean of its divisors is an integer number (61297040).

Almost surely, 2^661221077 is an apocalyptic number.

It is an amenable number.

661221077 is a deficient number, since it is larger than the sum of its proper divisors (74343403).

661221077 is a wasteful number, since it uses less digits than its factorization.

661221077 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65944 (or 65933 counting only the distinct ones).

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 661221077 is about 25714.2193542795. The cubic root of 661221077 is about 871.1953784233.

The spelling of 661221077 in words is "six hundred sixty-one million, two hundred twenty-one thousand, seventy-seven".