690291981 has 12 divisors (see below), whose sum is σ = 1015902108. Its totient is φ = 451511424.

The previous prime is 690291937. The next prime is 690291991. The reversal of 690291981 is 189192096.

It can be written as a sum of positive squares in 2 ways, for example, as 517790025 + 172501956 = 22755^2 + 13134^2 .

It is not a de Polignac number, because 690291981 - 2¹⁷ = 690160909 is a prime.

It is a super-2 number, since 2×690291981² = 953006038065808722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (690291991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 723100 + ... + 724053.

It is an arithmetic number, because the mean of its divisors is an integer number (84658509).

Almost surely, 2^690291981 is an apocalyptic number.

It is an amenable number.

690291981 is a deficient number, since it is larger than the sum of its proper divisors (325610127).

690291981 is a wasteful number, since it uses less digits than its factorization.

690291981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1447212 (or 1447209 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 45.

The square root of 690291981 is about 26273.4082486456. The cubic root of 690291981 is about 883.7802174861.

The spelling of 690291981 in words is "six hundred ninety million, two hundred ninety-one thousand, nine hundred eighty-one".