81220945 has 16 divisors (see below), whose sum is σ = 105799680. Its totient is φ = 59500224.

The previous prime is 81220939. The next prime is 81220973. The reversal of 81220945 is 54902218.

It is a cyclic number.

It is not a de Polignac number, because 81220945 - 2¹¹ = 81218897 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3336 + ... + 13174.

It is an arithmetic number, because the mean of its divisors is an integer number (6612480).

Almost surely, 2^81220945 is an apocalyptic number.

It is an amenable number.

81220945 is a deficient number, since it is larger than the sum of its proper divisors (24578735).

81220945 is a wasteful number, since it uses less digits than its factorization.

81220945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9984.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 81220945 is about 9012.2663631298. The cubic root of 81220945 is about 433.0679186645.

The spelling of 81220945 in words is "eighty-one million, two hundred twenty thousand, nine hundred forty-five".