745647781 has 4 divisors (see below), whose sum is σ = 749767564. Its totient is φ = 741528000.

The previous prime is 745647767. The next prime is 745647803. The reversal of 745647781 is 187746547.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 187746547 = 37 ⋅5074231.

It can be written as a sum of positive squares in 2 ways, for example, as 287302500 + 458345281 = 16950^2 + 21409^2 .

It is a cyclic number.

It is not a de Polignac number, because 745647781 - 2¹⁹ = 745123493 is a prime.

It is a super-2 number, since 2×745647781² = 1111981226620447922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (745647181) 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, 2059620 + ... + 2059981.

It is an arithmetic number, because the mean of its divisors is an integer number (187441891).

Almost surely, 2^745647781 is an apocalyptic number.

It is an amenable number.

745647781 is a deficient number, since it is larger than the sum of its proper divisors (4119783).

745647781 is a wasteful number, since it uses less digits than its factorization.

745647781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4119782.

The product of its digits is 1317120, while the sum is 49.

The square root of 745647781 is about 27306.5519793327. The cubic root of 745647781 is about 906.7994400033.

The spelling of 745647781 in words is "seven hundred forty-five million, six hundred forty-seven thousand, seven hundred eighty-one".