1221540231 has 4 divisors (see below), whose sum is σ = 1628720312. Its totient is φ = 814360152.

The previous prime is 1221540223. The next prime is 1221540241. The reversal of 1221540231 is 1320451221.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 1221540231 - 2³ = 1221540223 is a prime.

It is a super-2 number, since 2×1221540231² = 2984321071903066722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221540198 and 1221540207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221540241) 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, 203590036 + ... + 203590041.

It is an arithmetic number, because the mean of its divisors is an integer number (407180078).

Almost surely, 2^1221540231 is an apocalyptic number.

1221540231 is a deficient number, since it is larger than the sum of its proper divisors (407180081).

1221540231 is an equidigital number, since it uses as much as digits as its factorization.

1221540231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 407180080.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 1221540231 is about 34950.5397812394. The cubic root of 1221540231 is about 1068.9792084299.

Adding to 1221540231 its reverse (1320451221), we get a palindrome (2541991452).

The spelling of 1221540231 in words is "one billion, two hundred twenty-one million, five hundred forty thousand, two hundred thirty-one".