21351998381 has 12 divisors (see below), whose sum is σ = 25208759808. Its totient is φ = 18028550232.

The previous prime is 21351998377. The next prime is 21351998387. The reversal of 21351998381 is 18389915312.

It is not a de Polignac number, because 21351998381 - 2² = 21351998377 is a prime.

It is a super-2 number, since 2×21351998381² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21351998387) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3248621 + ... + 3255186.

It is an arithmetic number, because the mean of its divisors is an integer number (2100729984).

Almost surely, 2^21351998381 is an apocalyptic number.

It is an amenable number.

21351998381 is a deficient number, since it is larger than the sum of its proper divisors (3856761427).

21351998381 is an equidigital number, since it uses as much as digits as its factorization.

21351998381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6503888 (or 6503881 counting only the distinct ones).

The product of its digits is 466560, while the sum is 50.

The spelling of 21351998381 in words is "twenty-one billion, three hundred fifty-one million, nine hundred ninety-eight thousand, three hundred eighty-one".