21621421213456 has 15 divisors (see below), whose sum is σ = 41891539637703. Its totient is φ = 10810701306960.

The previous prime is 21621421213453. The next prime is 21621421213501. The reversal of 21621421213456 is 65431212412612.

The square root of 21621421213456 is 4649884.

It is a perfect power (a square), and thus also a powerful number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621421213451) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 18018301 + ... + 19180771.

Almost surely, 2^{21621421213456} is an apocalyptic number.

21621421213456 is the 4649884-th square number.

It is an amenable number.

21621421213456 is a deficient number, since it is larger than the sum of its proper divisors (20270118424247).

21621421213456 is an frugal number, since it uses more digits than its factorization.

21621421213456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2324950 (or 1162473 counting only the distinct ones).

The product of its digits is 138240, while the sum is 40.

The spelling of 21621421213456 in words is "twenty-one trillion, six hundred twenty-one billion, four hundred twenty-one million, two hundred thirteen thousand, four hundred fifty-six".