21258949 has 4 divisors (see below), whose sum is σ = 21389536. Its totient is φ = 21128364.

The previous prime is 21258917. The next prime is 21258973. The reversal of 21258949 is 94985212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21258949 - 2⁵ = 21258917 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21258649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65049 + ... + 65374.

It is an arithmetic number, because the mean of its divisors is an integer number (5347384).

Almost surely, 2^21258949 is an apocalyptic number.

It is an amenable number.

21258949 is a deficient number, since it is larger than the sum of its proper divisors (130587).

21258949 is a wasteful number, since it uses less digits than its factorization.

21258949 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130586.

The product of its digits is 51840, while the sum is 40.

The square root of 21258949 is about 4610.7427818086. The cubic root of 21258949 is about 277.0217892646.

The spelling of 21258949 in words is "twenty-one million, two hundred fifty-eight thousand, nine hundred forty-nine".