20856725642 has 4 divisors (see below), whose sum is σ = 31285088466. Its totient is φ = 10428362820.

The previous prime is 20856725639. The next prime is 20856725653. The reversal of 20856725642 is 24652765802.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 18171309601 + 2685416041 = 134801^2 + 51821^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5214181409 + ... + 5214181412.

Almost surely, 2^20856725642 is an apocalyptic number.

20856725642 is a deficient number, since it is larger than the sum of its proper divisors (10428362824).

20856725642 is a wasteful number, since it uses less digits than its factorization.

20856725642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10428362823.

The product of its (nonzero) digits is 1612800, while the sum is 47.

The spelling of 20856725642 in words is "twenty billion, eight hundred fifty-six million, seven hundred twenty-five thousand, six hundred forty-two".