21481690 has 16 divisors (see below), whose sum is σ = 39051720. Its totient is φ = 8507200.

The previous prime is 21481687. The next prime is 21481697. The reversal of 21481690 is 9618412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 21132409 + 349281 = 4597^2 + 591^2 .

It is a super-2 number, since 2×21481690² = 922926010512200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21481697) 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, 9625 + ... + 11644.

Almost surely, 2^21481690 is an apocalyptic number.

21481690 is a deficient number, since it is larger than the sum of its proper divisors (17570030).

21481690 is a wasteful number, since it uses less digits than its factorization.

21481690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21377.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21481690 is about 4634.8344091240. The cubic root of 21481690 is about 277.9859299678.

The spelling of 21481690 in words is "twenty-one million, four hundred eighty-one thousand, six hundred ninety".