21621258 has 24 divisors (see below), whose sum is σ = 47642400. Its totient is φ = 7084584.

The previous prime is 21621239. The next prime is 21621277. The reversal of 21621258 is 85212612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21621239) and next prime (21621277).

It is a Curzon number.

It is an unprimeable number.

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, 9118 + ... + 11241.

It is an arithmetic number, because the mean of its divisors is an integer number (1985100).

Almost surely, 2^21621258 is an apocalyptic number.

21621258 is an abundant number, since it is smaller than the sum of its proper divisors (26021142).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21621258 is a wasteful number, since it uses less digits than its factorization.

21621258 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20426 (or 20423 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 21621258 is about 4649.8664496951. The cubic root of 21621258 is about 278.5866620016.

The spelling of 21621258 in words is "twenty-one million, six hundred twenty-one thousand, two hundred fifty-eight".