61661220 has 24 divisors (see below), whose sum is σ = 172651584. Its totient is φ = 16442976.

The previous prime is 61661209. The next prime is 61661231. The reversal of 61661220 is 2216616.

It is an interprime number because it is at equal distance from previous prime (61661209) and next prime (61661231).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 513784 + ... + 513903.

It is an arithmetic number, because the mean of its divisors is an integer number (7193816).

Almost surely, 2^61661220 is an apocalyptic number.

61661220 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

61661220 is an abundant number, since it is smaller than the sum of its proper divisors (110990364).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

61661220 is a wasteful number, since it uses less digits than its factorization.

61661220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1027699 (or 1027697 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 61661220 is about 7852.4658547491. The cubic root of 61661220 is about 395.0669544143.

Adding to 61661220 its reverse (2216616), we get a palindrome (63877836).

The spelling of 61661220 in words is "sixty-one million, six hundred sixty-one thousand, two hundred twenty".