21421779840 has 96 divisors (see below), whose sum is σ = 73972103400. Its totient is φ = 5712473088.

The previous prime is 21421779829. The next prime is 21421779887. The reversal of 21421779840 is 4897712412.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1853770 + ... + 1865289.

Almost surely, 2^21421779840 is an apocalyptic number.

21421779840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21421779840 is an abundant number, since it is smaller than the sum of its proper divisors (52550323560).

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

21421779840 is a wasteful number, since it uses less digits than its factorization.

21421779840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3719084 (or 3719069 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 45.

The spelling of 21421779840 in words is "twenty-one billion, four hundred twenty-one million, seven hundred seventy-nine thousand, eight hundred forty".