81521070421 has 16 divisors (see below), whose sum is σ = 95606896000. Its totient is φ = 68054551488.

The previous prime is 81521070341. The next prime is 81521070443. The reversal of 81521070421 is 12407012518.

It is not a de Polignac number, because 81521070421 - 2⁹ = 81521069909 is a prime.

It is a super-2 number, since 2×81521070421² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81521070221) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 282966 + ... + 493063.

It is an arithmetic number, because the mean of its divisors is an integer number (5975431000).

Almost surely, 2^81521070421 is an apocalyptic number.

It is an amenable number.

81521070421 is a deficient number, since it is larger than the sum of its proper divisors (14085825579).

81521070421 is a wasteful number, since it uses less digits than its factorization.

81521070421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 776428.

The product of its (nonzero) digits is 4480, while the sum is 31.

Adding to 81521070421 its reverse (12407012518), we get a palindrome (93928082939).

The spelling of 81521070421 in words is "eighty-one billion, five hundred twenty-one million, seventy thousand, four hundred twenty-one".