21012870 has 16 divisors (see below), whose sum is σ = 50430960. Its totient is φ = 5603424.

The previous prime is 21012851. The next prime is 21012877. The reversal of 21012870 is 7821012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012877) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 350185 + ... + 350244.

It is an arithmetic number, because the mean of its divisors is an integer number (3151935).

Almost surely, 2^21012870 is an apocalyptic number.

21012870 is an abundant number, since it is smaller than the sum of its proper divisors (29418090).

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

21012870 is a wasteful number, since it uses less digits than its factorization.

21012870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 700439.

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 21012870 is about 4583.9797119970. The cubic root of 21012870 is about 275.9487670079.

Adding to 21012870 its reverse (7821012), we get a palindrome (28833882).

The spelling of 21012870 in words is "twenty-one million, twelve thousand, eight hundred seventy".