21251420542 has 64 divisors (see below), whose sum is σ = 36936000000. Its totient is φ = 9069096960.

The previous prime is 21251420521. The next prime is 21251420543. The reversal of 21251420542 is 24502415212.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21251420542.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251420543) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 37348434 + ... + 37349002.

It is an arithmetic number, because the mean of its divisors is an integer number (577125000).

Almost surely, 2^21251420542 is an apocalyptic number.

21251420542 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21251420542 is a deficient number, since it is larger than the sum of its proper divisors (15684579458).

21251420542 is a wasteful number, since it uses less digits than its factorization.

21251420542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1249.

The product of its (nonzero) digits is 6400, while the sum is 28.

Adding to 21251420542 its reverse (24502415212), we get a palindrome (45753835754).

The spelling of 21251420542 in words is "twenty-one billion, two hundred fifty-one million, four hundred twenty thousand, five hundred forty-two".