21061810 has 64 divisors (see below), whose sum is σ = 50077440. Its totient is φ = 6174720.

The previous prime is 21061783. The next prime is 21061819. The reversal of 21061810 is 1816012.

It is a super-2 number, since 2×21061810² = 887199680952200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21061819) 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, 12286 + ... + 13894.

It is an arithmetic number, because the mean of its divisors is an integer number (782460).

Almost surely, 2^21061810 is an apocalyptic number.

21061810 is an abundant number, since it is smaller than the sum of its proper divisors (29015630).

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

21061810 is a wasteful number, since it uses less digits than its factorization.

21061810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1651.

The product of its (nonzero) digits is 96, while the sum is 19.

The square root of 21061810 is about 4589.3147636657. The cubic root of 21061810 is about 276.1628336197.

Adding to 21061810 its reverse (1816012), we get a palindrome (22877822).

It can be divided in two parts, 2106 and 1810, that added together give a triangular number (3916 = T₈₈).

The spelling of 21061810 in words is "twenty-one million, sixty-one thousand, eight hundred ten".