405629981 has 4 divisors (see below), whose sum is σ = 405670812. Its totient is φ = 405589152.

The previous prime is 405629971. The next prime is 405630007. The reversal of 405629981 is 189926504.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 233784100 + 171845881 = 15290^2 + 13109^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-405629981 is a prime.

It is a super-2 number, since 2×405629981² = 329071362972120722, which 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 (405629951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5201 + ... + 28953.

It is an arithmetic number, because the mean of its divisors is an integer number (101417703).

Almost surely, 2^405629981 is an apocalyptic number.

It is an amenable number.

405629981 is a deficient number, since it is larger than the sum of its proper divisors (40831).

405629981 is a wasteful number, since it uses less digits than its factorization.

405629981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40830.

The product of its (nonzero) digits is 155520, while the sum is 44.

The square root of 405629981 is about 20140.2577193044. The cubic root of 405629981 is about 740.2470449815.

The spelling of 405629981 in words is "four hundred five million, six hundred twenty-nine thousand, nine hundred eighty-one".