691249861 has 4 divisors (see below), whose sum is σ = 691488000. Its totient is φ = 691011724.

The previous prime is 691249807. The next prime is 691249877. The reversal of 691249861 is 168942196.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 691249861 - 2¹³ = 691241669 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 (691249891) 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, 114661 + ... + 120538.

It is an arithmetic number, because the mean of its divisors is an integer number (172872000).

Almost surely, 2^691249861 is an apocalyptic number.

It is an amenable number.

691249861 is a deficient number, since it is larger than the sum of its proper divisors (238139).

691249861 is a wasteful number, since it uses less digits than its factorization.

691249861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238138.

The product of its digits is 186624, while the sum is 46.

The square root of 691249861 is about 26291.6310068432. The cubic root of 691249861 is about 884.1888195207.

The spelling of 691249861 in words is "six hundred ninety-one million, two hundred forty-nine thousand, eight hundred sixty-one".