61649640 has 128 divisors (see below), whose sum is σ = 221356800. Its totient is φ = 15171840.

The previous prime is 61649639. The next prime is 61649647. The reversal of 61649640 is 4694616.

61649640 is a `hidden beast` number, since 6 + 1 + 6 + 4 + 9 + 640 = 666.

It is a super-2 number, since 2×61649640² = 7601356224259200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 61649595 and 61649604.

It is not an unprimeable number, because it can be changed into a prime (61649647) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 11845 + ... + 16235.

It is an arithmetic number, because the mean of its divisors is an integer number (1729350).

Almost surely, 2^61649640 is an apocalyptic number.

61649640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 61649640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (110678400).

61649640 is an abundant number, since it is smaller than the sum of its proper divisors (159707160).

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

61649640 is a wasteful number, since it uses less digits than its factorization.

61649640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4424 (or 4414 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 61649640 is about 7851.7284721264. The cubic root of 61649640 is about 395.0422216257.

The spelling of 61649640 in words is "sixty-one million, six hundred forty-nine thousand, six hundred forty".