21000535251554 has 4 divisors (see below), whose sum is σ = 31500802877334. Its totient is φ = 10500267625776.

The previous prime is 21000535251539. The next prime is 21000535251559. The reversal of 21000535251554 is 45515253500012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20995136382025 + 5398869529 = 4582045^2 + 73477^2 .

It is not an unprimeable number, because it can be changed into a prime (21000535251559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250133812887 + ... + 5250133812890.

Almost surely, 2^{21000535251554} is an apocalyptic number.

21000535251554 is a deficient number, since it is larger than the sum of its proper divisors (10500267625780).

21000535251554 is a wasteful number, since it uses less digits than its factorization.

21000535251554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10500267625779.

The product of its (nonzero) digits is 150000, while the sum is 38.

Adding to 21000535251554 its reverse (45515253500012), we get a palindrome (66515788751566).

The spelling of 21000535251554 in words is "twenty-one trillion, five hundred thirty-five million, two hundred fifty-one thousand, five hundred fifty-four".