61651400209 has 27 divisors (see below), whose sum is σ = 72798369147. Its totient is φ = 52058942208.

The previous prime is 61651400197. The next prime is 61651400219. The reversal of 61651400209 is 90200415616.

The square root of 61651400209 is 248297.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 37675974609 + 23975425600 = 194103^2 + 154840^2 .

It is not a de Polignac number, because 61651400209 - 2⁵ = 61651400177 is a prime.

It is not an unprimeable number, because it can be changed into a prime (61651400219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 137308017 + ... + 137308465.

Almost surely, 2^61651400209 is an apocalyptic number.

61651400209 is the 248297-th square number.

61651400209 is the 124149-th centered octagonal number.

It is an amenable number.

61651400209 is a deficient number, since it is larger than the sum of its proper divisors (11146968938).

61651400209 is an frugal number, since it uses more digits than its factorization.

61651400209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1070 (or 535 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 34.

The spelling of 61651400209 in words is "sixty-one billion, six hundred fifty-one million, four hundred thousand, two hundred nine".