21261858 has 8 divisors (see below), whose sum is σ = 42523728. Its totient is φ = 7087284.

The previous prime is 21261839. The next prime is 21261869. The reversal of 21261858 is 85816212.

It is a sphenic number, since it is the product of 3 distinct primes.

21261858 is an admirable number.

It is a super-2 number, since 2×21261858² = 904133211224328, which contains 22 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1771816 + ... + 1771827.

It is an arithmetic number, because the mean of its divisors is an integer number (5315466).

Almost surely, 2^21261858 is an apocalyptic number.

21261858 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21261858 is a wasteful number, since it uses less digits than its factorization.

21261858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3543648.

The product of its digits is 7680, while the sum is 33.

The square root of 21261858 is about 4611.0582299511. The cubic root of 21261858 is about 277.0344242516.

The spelling of 21261858 in words is "twenty-one million, two hundred sixty-one thousand, eight hundred fifty-eight".