1561851377 has 4 divisors (see below), whose sum is σ = 1568386560. Its totient is φ = 1555316196.

The previous prime is 1561851307. The next prime is 1561851413. The reversal of 1561851377 is 7731581651.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7731581651 = 157 ⋅49245743.

It is a cyclic number.

It is not a de Polignac number, because 1561851377 - 2¹⁴ = 1561834993 is a prime.

It is a super-2 number, since 2×1561851377² = 4878759447673592258, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561851307) 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, 3267233 + ... + 3267710.

It is an arithmetic number, because the mean of its divisors is an integer number (392096640).

Almost surely, 2^1561851377 is an apocalyptic number.

It is an amenable number.

1561851377 is a deficient number, since it is larger than the sum of its proper divisors (6535183).

1561851377 is an equidigital number, since it uses as much as digits as its factorization.

1561851377 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6535182.

The product of its digits is 176400, while the sum is 44.

The square root of 1561851377 is about 39520.2653963761. The cubic root of 1561851377 is about 1160.2366186453.

The spelling of 1561851377 in words is "one billion, five hundred sixty-one million, eight hundred fifty-one thousand, three hundred seventy-seven".