20153981 has 8 divisors (see below), whose sum is σ = 20496504. Its totient is φ = 19814400.

The previous prime is 20153963. The next prime is 20153983. The reversal of 20153981 is 18935102.

It can be written as a sum of positive squares in 4 ways, for example, as 1092025 + 19061956 = 1045^2 + 4366^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20153981 is a prime.

It is a super-2 number, since 2×20153981² = 812365900296722, 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 (20153983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16181 + ... + 17381.

It is an arithmetic number, because the mean of its divisors is an integer number (2562063).

Almost surely, 2^20153981 is an apocalyptic number.

It is an amenable number.

20153981 is a deficient number, since it is larger than the sum of its proper divisors (342523).

20153981 is a wasteful number, since it uses less digits than its factorization.

20153981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1471.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 20153981 is about 4489.3185451692. The cubic root of 20153981 is about 272.1365960754.

The spelling of 20153981 in words is "twenty million, one hundred fifty-three thousand, nine hundred eighty-one".