91251220 has 12 divisors (see below), whose sum is σ = 191627604. Its totient is φ = 36500480.

The previous prime is 91251211. The next prime is 91251221. The reversal of 91251220 is 2215219.

It can be written as a sum of positive squares in 2 ways, for example, as 26255376 + 64995844 = 5124^2 + 8062^2 .

It is a junction number, because it is equal to n+sod(n) for n = 91251191 and 91251200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91251221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2281261 + ... + 2281300.

It is an arithmetic number, because the mean of its divisors is an integer number (15968967).

Almost surely, 2^91251220 is an apocalyptic number.

It is an amenable number.

91251220 is an abundant number, since it is smaller than the sum of its proper divisors (100376384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

91251220 is a wasteful number, since it uses less digits than its factorization.

91251220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4562570 (or 4562568 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 91251220 is about 9552.5504447765. The cubic root of 91251220 is about 450.2076736918.

Adding to 91251220 its reverse (2215219), we get a palindrome (93466439).

The spelling of 91251220 in words is "ninety-one million, two hundred fifty-one thousand, two hundred twenty".