21690457 has 16 divisors (see below), whose sum is σ = 23500800. Its totient is φ = 19958400.

The previous prime is 21690451. The next prime is 21690467. The reversal of 21690457 is 75409612.

It is a cyclic number.

It is not a de Polignac number, because 21690457 - 2⁷ = 21690329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21690451) 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 15 ways as a sum of consecutive naturals, for example, 170728 + ... + 170854.

It is an arithmetic number, because the mean of its divisors is an integer number (1468800).

Almost surely, 2^21690457 is an apocalyptic number.

It is an amenable number.

21690457 is a deficient number, since it is larger than the sum of its proper divisors (1810343).

21690457 is a wasteful number, since it uses less digits than its factorization.

21690457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21690457 is about 4657.3014718826. The cubic root of 21690457 is about 278.8835517345.

The spelling of 21690457 in words is "twenty-one million, six hundred ninety thousand, four hundred fifty-seven".