1220156551 has 4 divisors (see below), whose sum is σ = 1220227272. Its totient is φ = 1220085832.

The previous prime is 1220156533. The next prime is 1220156569. The reversal of 1220156551 is 1556510221.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (1220156533) and next prime (1220156569).

It is a cyclic number.

It is not a de Polignac number, because 1220156551 - 2¹³ = 1220148359 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1220156591) 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, 9441 + ... + 50293.

It is an arithmetic number, because the mean of its divisors is an integer number (305056818).

Almost surely, 2^1220156551 is an apocalyptic number.

1220156551 is a deficient number, since it is larger than the sum of its proper divisors (70721).

1220156551 is an equidigital number, since it uses as much as digits as its factorization.

1220156551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70720.

The product of its (nonzero) digits is 3000, while the sum is 28.

The square root of 1220156551 is about 34930.7393423042. The cubic root of 1220156551 is about 1068.5754329476.

Adding to 1220156551 its reverse (1556510221), we get a palindrome (2776666772).

The spelling of 1220156551 in words is "one billion, two hundred twenty million, one hundred fifty-six thousand, five hundred fifty-one".