61215919861 has 4 divisors (see below), whose sum is σ = 64437810400. Its totient is φ = 57994029324.

The previous prime is 61215919811. The next prime is 61215919867. The reversal of 61215919861 is 16891951216.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 61215919861 - 2¹⁷ = 61215788789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61215919867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1610945241 + ... + 1610945278.

It is an arithmetic number, because the mean of its divisors is an integer number (16109452600).

Almost surely, 2^61215919861 is an apocalyptic number.

It is an amenable number.

61215919861 is a deficient number, since it is larger than the sum of its proper divisors (3221890539).

61215919861 is a wasteful number, since it uses less digits than its factorization.

61215919861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3221890538.

The product of its digits is 233280, while the sum is 49.

The spelling of 61215919861 in words is "sixty-one billion, two hundred fifteen million, nine hundred nineteen thousand, eight hundred sixty-one".