81228989978 has 16 divisors (see below), whose sum is σ = 124152156000. Its totient is φ = 39847643952.

The previous prime is 81228989923. The next prime is 81228989983. The reversal of 81228989978 is 87998982218.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 616148 + ... + 736271.

It is an arithmetic number, because the mean of its divisors is an integer number (7759509750).

Almost surely, 2^81228989978 is an apocalyptic number.

81228989978 is a deficient number, since it is larger than the sum of its proper divisors (42923166022).

81228989978 is a wasteful number, since it uses less digits than its factorization.

81228989978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1352989.

The product of its digits is 83607552, while the sum is 71.

Adding to 81228989978 its sum of digits (71), we get a square (81228990049 = 285007²).

The spelling of 81228989978 in words is "eighty-one billion, two hundred twenty-eight million, nine hundred eighty-nine thousand, nine hundred seventy-eight".