61561640 has 80 divisors (see below), whose sum is σ = 161841780. Its totient is φ = 21073920.

The previous prime is 61561631. The next prime is 61561649. The reversal of 61561640 is 4616516.

It is an interprime number because it is at equal distance from previous prime (61561631) and next prime (61561649).

It can be written as a sum of positive squares in 2 ways, for example, as 59938564 + 1623076 = 7742^2 + 1274^2 .

It is not an unprimeable number, because it can be changed into a prime (61561649) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 95720 + ... + 96360.

Almost surely, 2^61561640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 61561640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (80920890).

61561640 is an abundant number, since it is smaller than the sum of its proper divisors (100280140).

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

61561640 is an equidigital number, since it uses as much as digits as its factorization.

61561640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 680 (or 655 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 61561640 is about 7846.1226092893. The cubic root of 61561640 is about 394.8541682462.

The spelling of 61561640 in words is "sixty-one million, five hundred sixty-one thousand, six hundred forty".