20421870 has 64 divisors (see below), whose sum is σ = 57839616. Its totient is φ = 4515840.

The previous prime is 20421859. The next prime is 20421871. The reversal of 20421870 is 7812402.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 20421870.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20421871) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4942 + ... + 8078.

It is an arithmetic number, because the mean of its divisors is an integer number (903744).

Almost surely, 2^20421870 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20421870, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28919808).

20421870 is an abundant number, since it is smaller than the sum of its proper divisors (37417746).

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

20421870 is a wasteful number, since it uses less digits than its factorization.

20421870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3185.

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 20421870 is about 4519.0563174185. The cubic root of 20421870 is about 273.3370496553.

The spelling of 20421870 in words is "twenty million, four hundred twenty-one thousand, eight hundred seventy".