81921402 has 64 divisors (see below), whose sum is σ = 194088960. Its totient is φ = 25523712.

The previous prime is 81921401. The next prime is 81921421. The reversal of 81921402 is 20412918.

It is a super-2 number, since 2×81921402² = 13422232211291208, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (81921401) 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, 213703 + ... + 214085.

It is an arithmetic number, because the mean of its divisors is an integer number (3032640).

Almost surely, 2^81921402 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81921402, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97044480).

81921402 is an abundant number, since it is smaller than the sum of its proper divisors (112167558).

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

81921402 is a wasteful number, since it uses less digits than its factorization.

81921402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 644 (or 638 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 81921402 is about 9051.0442491461. The cubic root of 81921402 is about 434.3092962540.

The spelling of 81921402 in words is "eighty-one million, nine hundred twenty-one thousand, four hundred two".