51351665642 has 4 divisors (see below), whose sum is σ = 77027498466. Its totient is φ = 25675832820.

The previous prime is 51351665627. The next prime is 51351665699. The reversal of 51351665642 is 24656615315.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 24656615315 = 5 ⋅4931323063.

It can be written as a sum of positive squares in only one way, i.e., 28845965281 + 22505700361 = 169841^2 + 150019^2 .

It is a junction number, because it is equal to n+sod(n) for n = 51351665593 and 51351665602.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12837916409 + ... + 12837916412.

Almost surely, 2^51351665642 is an apocalyptic number.

51351665642 is a deficient number, since it is larger than the sum of its proper divisors (25675832824).

51351665642 is a wasteful number, since it uses less digits than its factorization.

51351665642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25675832823.

The product of its digits is 648000, while the sum is 44.

The spelling of 51351665642 in words is "fifty-one billion, three hundred fifty-one million, six hundred sixty-five thousand, six hundred forty-two".