77721540 has 48 divisors (see below), whose sum is σ = 234362688. Its totient is φ = 19131264.

The previous prime is 77721517. The next prime is 77721547. The reversal of 77721540 is 4512777.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (77721547) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49042 + ... + 50601.

It is an arithmetic number, because the mean of its divisors is an integer number (4882556).

Almost surely, 2^77721540 is an apocalyptic number.

It is an amenable number.

77721540 is an abundant number, since it is smaller than the sum of its proper divisors (156641148).

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

77721540 is a wasteful number, since it uses less digits than its factorization.

77721540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99668 (or 99666 counting only the distinct ones).

The product of its (nonzero) digits is 13720, while the sum is 33.

The square root of 77721540 is about 8815.9820780217. The cubic root of 77721540 is about 426.7568155326.

The spelling of 77721540 in words is "seventy-seven million, seven hundred twenty-one thousand, five hundred forty".