21029861 has 4 divisors (see below), whose sum is σ = 21088800.
Its totient is φ = 20970924.
The previous prime is 21029857. The next prime is 21029951. The reversal of 21029861 is 16892012.
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 21029861 - 22 = 21029857 is a prime.
It is a Duffinian number.
It is a Curzon number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (21029831) 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, 28931 + ... + 29648.
It is an arithmetic number, because the mean of its divisors is an integer number (5272200).
Almost surely, 221029861 is an apocalyptic number.
It is an amenable number.
21029861 is a deficient number, since it is larger than the sum of its proper divisors (58939).
21029861 is an equidigital number, since it uses as much as digits as its factorization.
21029861 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 58938.
The product of its (nonzero) digits is 1728, while the sum is 29.
The square root of 21029861 is about 4585.8326397722.
The cubic root of 21029861 is about 276.0231243315.
The spelling of 21029861 in words is "twenty-one million, twenty-nine thousand, eight hundred sixty-one".