61721499645 has 48 divisors (see below), whose sum is σ = 115388490672. Its totient is φ = 30339809280.

The previous prime is 61721499629. The next prime is 61721499727. The reversal of 61721499645 is 54699412716.

61721499645 is a `hidden beast` number, since 617 + 2 + 14 + 9 + 9 + 6 + 4 + 5 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 14004592281 + 47716907364 = 118341^2 + 218442^2 .

It is not a de Polignac number, because 61721499645 - 2⁴ = 61721499629 is a prime.

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 61721499591 and 61721499600.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 306877 + ... + 466493.

It is an arithmetic number, because the mean of its divisors is an integer number (2403926889).

Almost surely, 2^61721499645 is an apocalyptic number.

61721499645 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

61721499645 is a deficient number, since it is larger than the sum of its proper divisors (53666991027).

61721499645 is a wasteful number, since it uses less digits than its factorization.

61721499645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160302 (or 160299 counting only the distinct ones).

The product of its digits is 3265920, while the sum is 54.

The spelling of 61721499645 in words is "sixty-one billion, seven hundred twenty-one million, four hundred ninety-nine thousand, six hundred forty-five".