21961212 has 144 divisors (see below), whose sum is σ = 68372640. Its totient is φ = 5451264.

The previous prime is 21961187. The next prime is 21961243. The reversal of 21961212 is 21216912.

It is a hoax number, since the sum of its digits (24) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1291828 + ... + 1291844.

It is an arithmetic number, because the mean of its divisors is an integer number (474810).

Almost surely, 2^21961212 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21961212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34186320).

21961212 is an abundant number, since it is smaller than the sum of its proper divisors (46411428).

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

21961212 is a wasteful number, since it uses less digits than its factorization.

21961212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77 (or 42 counting only the distinct ones).

The product of its digits is 432, while the sum is 24.

The square root of 21961212 is about 4686.2791210085. The cubic root of 21961212 is about 280.0391611893.

The spelling of 21961212 in words is "twenty-one million, nine hundred sixty-one thousand, two hundred twelve".