81284617642 has 4 divisors (see below), whose sum is σ = 121926926466. Its totient is φ = 40642308820.

The previous prime is 81284617639. The next prime is 81284617657. The reversal of 81284617642 is 24671648218.

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., 69431723001 + 11852894641 = 263499^2 + 108871^2 .

It is a super-2 number, since 2×81284617642² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20321154409 + ... + 20321154412.

Almost surely, 2^81284617642 is an apocalyptic number.

81284617642 is a deficient number, since it is larger than the sum of its proper divisors (40642308824).

81284617642 is a wasteful number, since it uses less digits than its factorization.

81284617642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40642308823.

The product of its digits is 1032192, while the sum is 49.

The spelling of 81284617642 in words is "eighty-one billion, two hundred eighty-four million, six hundred seventeen thousand, six hundred forty-two".