1221520647 has 16 divisors (see below), whose sum is σ = 1664640000. Its totient is φ = 796401312.

The previous prime is 1221520631. The next prime is 1221520679. The reversal of 1221520647 is 7460251221.

It is not a de Polignac number, because 1221520647 - 2⁴ = 1221520631 is a prime.

It is a super-2 number, since 2×1221520647² = 2984225382094597218, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221520747) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 241854 + ... + 246852.

It is an arithmetic number, because the mean of its divisors is an integer number (104040000).

Almost surely, 2^1221520647 is an apocalyptic number.

1221520647 is a deficient number, since it is larger than the sum of its proper divisors (443119353).

1221520647 is a wasteful number, since it uses less digits than its factorization.

1221520647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6782.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 1221520647 is about 34950.2596127697. The cubic root of 1221520647 is about 1068.9734956966.

Adding to 1221520647 its reverse (7460251221), we get a palindrome (8681771868).

The spelling of 1221520647 in words is "one billion, two hundred twenty-one million, five hundred twenty thousand, six hundred forty-seven".