21457990 has 32 divisors (see below), whose sum is σ = 39626496. Its totient is φ = 8364000.

The previous prime is 21457981. The next prime is 21457993. The reversal of 21457990 is 9975412.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21457993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 85365 + ... + 85615.

It is an arithmetic number, because the mean of its divisors is an integer number (1238328).

Almost surely, 2^21457990 is an apocalyptic number.

21457990 is a deficient number, since it is larger than the sum of its proper divisors (18168506).

21457990 is a wasteful number, since it uses less digits than its factorization.

21457990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 444.

The product of its (nonzero) digits is 22680, while the sum is 37.

The square root of 21457990 is about 4632.2769779019. The cubic root of 21457990 is about 277.8836616191.

The spelling of 21457990 in words is "twenty-one million, four hundred fifty-seven thousand, nine hundred ninety".