21212104 has 8 divisors (see below), whose sum is σ = 39772710. Its totient is φ = 10606048.

The previous prime is 21212101. The next prime is 21212111. The reversal of 21212104 is 40121212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20232004 + 980100 = 4498^2 + 990^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-3 number, since 3×21212104³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21212101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1325749 + ... + 1325764.

Almost surely, 2^21212104 is an apocalyptic number.

It is an amenable number.

21212104 is a deficient number, since it is larger than the sum of its proper divisors (18560606).

21212104 is a wasteful number, since it uses less digits than its factorization.

21212104 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2651519 (or 2651515 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21212104 is about 4605.6599961352. The cubic root of 21212104 is about 276.8181631861.

Adding to 21212104 its reverse (40121212), we get a palindrome (61333316).

It can be divided in two parts, 21212 and 104, that added together give a square (21316 = 146²).

The spelling of 21212104 in words is "twenty-one million, two hundred twelve thousand, one hundred four".