21246621520 has 20 divisors (see below), whose sum is σ = 49398395220. Its totient is φ = 8498648576.

The previous prime is 21246621491. The next prime is 21246621533. The reversal of 21246621520 is 2512664212.

It can be written as a sum of positive squares in 2 ways, for example, as 14749616704 + 6497004816 = 121448^2 + 80604^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×21246621520² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132791305 + ... + 132791464.

It is an arithmetic number, because the mean of its divisors is an integer number (2469919761).

Almost surely, 2^21246621520 is an apocalyptic number.

21246621520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21246621520 is an abundant number, since it is smaller than the sum of its proper divisors (28151773700).

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

21246621520 is a wasteful number, since it uses less digits than its factorization.

21246621520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265582782 (or 265582776 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 31.

The spelling of 21246621520 in words is "twenty-one billion, two hundred forty-six million, six hundred twenty-one thousand, five hundred twenty".