61721601648 has 160 divisors (see below), whose sum is σ = 188827533312. Its totient is φ = 17000236800.

The previous prime is 61721601647. The next prime is 61721601691. The reversal of 61721601648 is 84610612716.

It is a super-2 number, since 2×61721601648² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61721601647) 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, 2728143 + ... + 2750673.

Almost surely, 2^61721601648 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 61721601648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (94413766656).

61721601648 is an abundant number, since it is smaller than the sum of its proper divisors (127105931664).

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

61721601648 is a wasteful number, since it uses less digits than its factorization.

61721601648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22843 (or 22837 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 42.

The spelling of 61721601648 in words is "sixty-one billion, seven hundred twenty-one million, six hundred one thousand, six hundred forty-eight".