5651991 has 8 divisors (see below), whose sum is σ = 8373360. Its totient is φ = 3767976.

The previous prime is 5651983. The next prime is 5651999. The reversal of 5651991 is 1991565.

5651991 is a `hidden beast` number, since 56 + 519 + 91 = 666.

It is an interprime number because it is at equal distance from previous prime (5651983) and next prime (5651999).

It is not a de Polignac number, because 5651991 - 2³ = 5651983 is a prime.

5651991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (5651999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 104640 + ... + 104693.

It is an arithmetic number, because the mean of its divisors is an integer number (1046670).

Almost surely, 2^5651991 is an apocalyptic number.

5651991 is a deficient number, since it is larger than the sum of its proper divisors (2721369).

5651991 is a wasteful number, since it uses less digits than its factorization.

5651991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209342 (or 209336 counting only the distinct ones).

The product of its digits is 12150, while the sum is 36.

The square root of 5651991 is about 2377.3916379091. The cubic root of 5651991 is about 178.1286680685.

It can be divided in two parts, 565 and 1991, that added together give a triangular number (2556 = T₇₁).

The spelling of 5651991 in words is "five million, six hundred fifty-one thousand, nine hundred ninety-one".