918756721 has 9 divisors (see below), whose sum is σ = 976528011. Its totient is φ = 864227232.

The previous prime is 918756719. The next prime is 918756763. The reversal of 918756721 is 127657819.

It is a happy number.

The square root of 918756721 is 30311.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 715295025 + 203461696 = 26745^2 + 14264^2 .

It is not a de Polignac number, because 918756721 - 2¹ = 918756719 is a prime.

It is a super-2 number, since 2×918756721² = 1688227824765343682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (918756121) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 514396 + ... + 516178.

Almost surely, 2^918756721 is an apocalyptic number.

918756721 is the 30311-st square number.

918756721 is the 15156-th centered octagonal number.

It is an amenable number.

918756721 is a deficient number, since it is larger than the sum of its proper divisors (57771290).

918756721 is an frugal number, since it uses more digits than its factorization.

918756721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3600 (or 1800 counting only the distinct ones).

The product of its digits is 211680, while the sum is 46.

The cubic root of 918756721 is about 972.1505130404.

It can be divided in two parts, 91875 and 6721, that added together give a square (98596 = 314²).

The spelling of 918756721 in words is "nine hundred eighteen million, seven hundred fifty-six thousand, seven hundred twenty-one".