81220851 has 24 divisors (see below), whose sum is σ = 124204080. Its totient is φ = 51057216.

The previous prime is 81220823. The next prime is 81220859. The reversal of 81220851 is 15802218.

81220851 = 929² + 930² + ... + 1014².

It is not a de Polignac number, because 81220851 - 2⁶ = 81220787 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81220859) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7605 + ... + 14841.

It is an arithmetic number, because the mean of its divisors is an integer number (5175170).

Almost surely, 2^81220851 is an apocalyptic number.

81220851 is a deficient number, since it is larger than the sum of its proper divisors (42983229).

81220851 is a wasteful number, since it uses less digits than its factorization.

81220851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7315 (or 7312 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 81220851 is about 9012.2611480139. The cubic root of 81220851 is about 433.0677515959.

The spelling of 81220851 in words is "eighty-one million, two hundred twenty thousand, eight hundred fifty-one".