61661661152621 has 4 divisors (see below), whose sum is σ = 61661693855292. Its totient is φ = 61661628449952.

The previous prime is 61661661152603. The next prime is 61661661152653. The reversal of 61661661152621 is 12625116616616.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20646218403721 + 41015442748900 = 4543811^2 + 6404330^2 .

It is a cyclic number.

It is not a de Polignac number, because 61661661152621 - 2¹⁴ = 61661661136237 is a prime.

It is a super-2 number, since 2×61661661152621² (a number of 28 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 61661661152621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61661661152671) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13337936 + ... + 17355801.

It is an arithmetic number, because the mean of its divisors is an integer number (15415423463823).

Almost surely, 2^{61661661152621} is an apocalyptic number.

It is an amenable number.

61661661152621 is a deficient number, since it is larger than the sum of its proper divisors (32702671).

61661661152621 is a wasteful number, since it uses less digits than its factorization.

61661661152621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32702670.

The product of its digits is 933120, while the sum is 50.

The spelling of 61661661152621 in words is "sixty-one trillion, six hundred sixty-one billion, six hundred sixty-one million, one hundred fifty-two thousand, six hundred twenty-one".