1551056561 has 4 divisors (see below), whose sum is σ = 1604541300. Its totient is φ = 1497571824.

The previous prime is 1551056467. The next prime is 1551056599. The reversal of 1551056561 is 1656501551.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1656501551 = 11813 ⋅140227.

It can be written as a sum of positive squares in 2 ways, for example, as 411318961 + 1139737600 = 20281^2 + 33760^2 .

It is a cyclic number.

It is not a de Polignac number, because 1551056561 - 2³⁰ = 477314737 is a prime.

It is a super-2 number, since 2×1551056561² = 4811552910842293442, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1551050561) 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, 26742326 + ... + 26742383.

It is an arithmetic number, because the mean of its divisors is an integer number (401135325).

Almost surely, 2^1551056561 is an apocalyptic number.

It is an amenable number.

1551056561 is a deficient number, since it is larger than the sum of its proper divisors (53484739).

1551056561 is an equidigital number, since it uses as much as digits as its factorization.

1551056561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53484738.

The product of its (nonzero) digits is 22500, while the sum is 35.

The square root of 1551056561 is about 39383.4554222963. The cubic root of 1551056561 is about 1157.5574250130.

The spelling of 1551056561 in words is "one billion, five hundred fifty-one million, fifty-six thousand, five hundred sixty-one".